MATH
-   IS
------
   FUN

Given each alphabet is a digit, what are the possible solutions ?

(Don't scroll down if you want to give it a shot)





























Haskell in GHCI:

[(m,a,t,h,i,s,f,u,n)|m <- [0..9], a <- [0..9], t <- [0..9], h <- [0..9], i <- [0..9], s <- [0..9], f <- [0..9], u <- [0..9], n <- [0..9], (m*1000+a*100+t*10+h) - (i*10+s) == f*100+u*10+n, not (elem m [a,t,h,i,s,f,u,n]), not (elem a [t,h,i,s,f,u,n]), not (elem t [h,i,s,f,u,n]), not (elem h [i,s,f,u,n]), not (elem i [s,f,u,n]), not (elem s [f,u,n]), not (elem f [u,n]), not (u==n)]

Alternatively, a much faster version (in a main.hs for example):

module Main where
main :: IO ()
main = putStrLn (show 
    [(m,a,t,h,i,s,f,u,n)
    | m <- [0..9],
      a <- remove m [0..9],
      t <- remove' [m,a] [0..9],
      h <- remove' [m,a,t] [0..9],
      i <- remove' [m,a,t,h] [0..9],
      s <- remove' [m,a,t,h,i] [0..9],
      f <- remove' [m,a,t,h,i,s] [0..9],
      u <- remove' [m,a,t,h,i,s,f] [0..9],
      n <- remove' [m,a,t,h,i,s,f,u] [0..9],
      (m*1000+a*100+t*10+h) - (i*10+s) == f*100+u*10+n
    ])
    
-- remove an element once from the list
remove :: (Eq a) => a -> [a] -> [a]
remove _ [] = []
remove a (x:xs)
    | a == x = xs
    | otherwise = [x] ++ (remove a xs)
    
-- remove each element in the removal list once from the target list
remove' ::  (Eq a) => [a] -> [a] -> [a]
remove' _ [] = []
remove' [] xs = xs
remove' (a:as) bs = remove' as (remove a bs)

360 solutions:

M,A,T,H,I,S,F,U,N
0,2,3,4,5,6,1,7,8
0,2,3,4,5,8,1,7,6
0,2,3,4,7,6,1,5,8
0,2,3,4,7,8,1,5,6
0,2,3,5,4,6,1,8,9
0,2,3,5,4,9,1,8,6
0,2,3,5,8,6,1,4,9
0,2,3,5,8,9,1,4,6
0,2,3,6,4,7,1,8,9
0,2,3,6,4,9,1,8,7
0,2,3,6,8,7,1,4,9
0,2,3,6,8,9,1,4,7
0,2,3,9,6,4,1,7,5
0,2,3,9,6,5,1,7,4
0,2,3,9,7,4,1,6,5
0,2,3,9,7,5,1,6,4
0,2,4,3,5,6,1,8,7
0,2,4,3,5,7,1,8,6
0,2,4,3,6,5,1,7,8
0,2,4,3,6,8,1,7,5
0,2,4,3,7,5,1,6,8
0,2,4,3,7,8,1,6,5
0,2,4,3,8,6,1,5,7
0,2,4,3,8,7,1,5,6
0,2,4,6,5,7,1,8,9
0,2,4,6,5,9,1,8,7
0,2,4,6,8,7,1,5,9
0,2,4,6,8,9,1,5,7
0,2,5,3,6,4,1,8,9
0,2,5,3,6,9,1,8,4
0,2,5,3,8,4,1,6,9
0,2,5,3,8,9,1,6,4
0,2,5,7,6,3,1,9,4
0,2,5,7,6,4,1,9,3
0,2,5,7,9,3,1,6,4
0,2,5,7,9,4,1,6,3
0,2,5,9,7,3,1,8,6
0,2,5,9,7,6,1,8,3
0,2,5,9,8,3,1,7,6
0,2,5,9,8,6,1,7,3
0,2,6,3,7,4,1,8,9
0,2,6,3,7,9,1,8,4
0,2,6,3,8,4,1,7,9
0,2,6,3,8,9,1,7,4
0,2,6,4,7,5,1,8,9
0,2,6,4,7,9,1,8,5
0,2,6,4,8,5,1,7,9
0,2,6,4,8,9,1,7,5
0,2,6,8,7,3,1,9,5
0,2,6,8,7,5,1,9,3
0,2,6,8,9,3,1,7,5
0,2,6,8,9,5,1,7,3
0,3,1,5,4,7,2,6,8
0,3,1,5,4,8,2,6,7
0,3,1,5,6,7,2,4,8
0,3,1,5,6,8,2,4,7
0,3,1,7,4,8,2,6,9
0,3,1,7,4,9,2,6,8
0,3,1,7,6,8,2,4,9
0,3,1,7,6,9,2,4,8
0,3,4,6,5,7,2,8,9
0,3,4,6,5,9,2,8,7
0,3,4,6,8,7,2,5,9
0,3,4,6,8,9,2,5,7
0,3,4,7,5,1,2,9,6
0,3,4,7,5,6,2,9,1
0,3,4,7,9,1,2,5,6
0,3,4,7,9,6,2,5,1
0,3,4,8,5,1,2,9,7
0,3,4,8,5,7,2,9,1
0,3,4,8,9,1,2,5,7
0,3,4,8,9,7,2,5,1
0,3,5,1,6,4,2,8,7
0,3,5,1,6,7,2,8,4
0,3,5,1,8,4,2,6,7
0,3,5,1,8,7,2,6,4
0,3,5,8,6,1,2,9,7
0,3,5,8,6,7,2,9,1
0,3,5,8,9,1,2,6,7
0,3,5,8,9,7,2,6,1
0,3,6,4,7,5,2,8,9
0,3,6,4,7,9,2,8,5
0,3,6,4,8,5,2,7,9
0,3,6,4,8,9,2,7,5
0,3,6,5,7,1,2,9,4
0,3,6,5,7,4,2,9,1
0,3,6,5,9,1,2,7,4
0,3,6,5,9,4,2,7,1
0,3,7,5,8,1,2,9,4
0,3,7,5,8,4,2,9,1
0,3,7,5,9,1,2,8,4
0,3,7,5,9,4,2,8,1
0,3,7,6,8,1,2,9,5
0,3,7,6,8,5,2,9,1
0,3,7,6,9,1,2,8,5
0,3,7,6,9,5,2,8,1
0,4,1,5,2,6,3,8,9
0,4,1,5,2,9,3,8,6
0,4,1,5,8,6,3,2,9
0,4,1,5,8,9,3,2,6
0,4,1,6,2,7,3,8,9
0,4,1,6,2,9,3,8,7
0,4,1,6,8,7,3,2,9
0,4,1,6,8,9,3,2,7
0,4,1,9,5,2,3,6,7
0,4,1,9,5,7,3,6,2
0,4,1,9,6,2,3,5,7
0,4,1,9,6,7,3,5,2
0,4,2,7,5,8,3,6,9
0,4,2,7,5,9,3,6,8
0,4,2,7,6,8,3,5,9
0,4,2,7,6,9,3,5,8
0,4,2,9,5,1,3,7,8
0,4,2,9,5,8,3,7,1
0,4,2,9,7,1,3,5,8
0,4,2,9,7,8,3,5,1
0,4,5,1,6,2,3,8,9
0,4,5,1,6,9,3,8,2
0,4,5,1,8,2,3,6,9
0,4,5,1,8,9,3,6,2
0,4,5,8,6,1,3,9,7
0,4,5,8,6,7,3,9,1
0,4,5,8,9,1,3,6,7
0,4,5,8,9,7,3,6,1
0,4,6,1,7,2,3,8,9
0,4,6,1,7,9,3,8,2
0,4,6,1,8,2,3,7,9
0,4,6,1,8,9,3,7,2
0,4,7,6,8,1,3,9,5
0,4,7,6,8,5,3,9,1
0,4,7,6,9,1,3,8,5
0,4,7,6,9,5,3,8,1
0,5,1,3,2,6,4,8,7
0,5,1,3,2,7,4,8,6
0,5,1,3,8,6,4,2,7
0,5,1,3,8,7,4,2,6
0,5,1,6,2,7,4,8,9
0,5,1,6,2,9,4,8,7
0,5,1,6,8,7,4,2,9
0,5,1,6,8,9,4,2,7
0,5,1,9,3,2,4,8,7
0,5,1,9,3,7,4,8,2
0,5,1,9,8,2,4,3,7
0,5,1,9,8,7,4,3,2
0,5,2,6,3,7,4,8,9
0,5,2,6,3,9,4,8,7
0,5,2,6,8,7,4,3,9
0,5,2,6,8,9,4,3,7
0,5,2,7,3,1,4,9,6
0,5,2,7,3,6,4,9,1
0,5,2,7,9,1,4,3,6
0,5,2,7,9,6,4,3,1
0,5,2,8,3,1,4,9,7
0,5,2,8,3,7,4,9,1
0,5,2,8,9,1,4,3,7
0,5,2,8,9,7,4,3,1
0,5,3,9,6,1,4,7,8
0,5,3,9,6,8,4,7,1
0,5,3,9,7,1,4,6,8
0,5,3,9,7,8,4,6,1
0,5,6,1,7,2,4,8,9
0,5,6,1,7,9,4,8,2
0,5,6,1,8,2,4,7,9
0,5,6,1,8,9,4,7,2
0,5,6,2,7,3,4,8,9
0,5,6,2,7,9,4,8,3
0,5,6,2,8,3,4,7,9
0,5,6,2,8,9,4,7,3
0,5,6,3,7,1,4,9,2
0,5,6,3,7,2,4,9,1
0,5,6,3,9,1,4,7,2
0,5,6,3,9,2,4,7,1
0,5,7,3,8,1,4,9,2
0,5,7,3,8,2,4,9,1
0,5,7,3,9,1,4,8,2
0,5,7,3,9,2,4,8,1
0,6,1,2,3,4,5,7,8
0,6,1,2,3,8,5,7,4
0,6,1,2,7,4,5,3,8
0,6,1,2,7,8,5,3,4
0,6,1,3,2,4,5,8,9
0,6,1,3,2,9,5,8,4
0,6,1,3,8,4,5,2,9
0,6,1,3,8,9,5,2,4
0,6,1,7,2,3,5,9,4
0,6,1,7,2,4,5,9,3
0,6,1,7,9,3,5,2,4
0,6,1,7,9,4,5,2,3
0,6,1,9,3,2,5,8,7
0,6,1,9,3,7,5,8,2
0,6,1,9,8,2,5,3,7
0,6,1,9,8,7,5,3,2
0,6,2,1,3,4,5,8,7
0,6,2,1,3,7,5,8,4
0,6,2,1,4,3,5,7,8
0,6,2,1,4,8,5,7,3
0,6,2,1,7,3,5,4,8
0,6,2,1,7,8,5,4,3
0,6,2,1,8,4,5,3,7
0,6,2,1,8,7,5,3,4
0,6,2,8,3,1,5,9,7
0,6,2,8,3,7,5,9,1
0,6,2,8,9,1,5,3,7
0,6,2,8,9,7,5,3,1
0,6,3,1,4,2,5,8,9
0,6,3,1,4,9,5,8,2
0,6,3,1,8,2,5,4,9
0,6,3,1,8,9,5,4,2
0,6,3,8,4,1,5,9,7
0,6,3,8,4,7,5,9,1
0,6,3,8,9,1,5,4,7
0,6,3,8,9,7,5,4,1
0,6,7,3,8,1,5,9,2
0,6,7,3,8,2,5,9,1
0,6,7,3,9,1,5,8,2
0,6,7,3,9,2,5,8,1
0,6,7,4,8,1,5,9,3
0,6,7,4,8,3,5,9,1
0,6,7,4,9,1,5,8,3
0,6,7,4,9,3,5,8,1
0,7,1,3,2,4,6,8,9
0,7,1,3,2,9,6,8,4
0,7,1,3,8,4,6,2,9
0,7,1,3,8,9,6,2,4
0,7,1,4,2,5,6,8,9
0,7,1,4,2,9,6,8,5
0,7,1,4,8,5,6,2,9
0,7,1,4,8,9,6,2,5
0,7,1,8,2,3,6,9,5
0,7,1,8,2,5,6,9,3
0,7,1,8,9,3,6,2,5
0,7,1,8,9,5,6,2,3
0,7,1,9,3,4,6,8,5
0,7,1,9,3,5,6,8,4
0,7,1,9,8,4,6,3,5
0,7,1,9,8,5,6,3,4
0,7,2,4,3,5,6,8,9
0,7,2,4,3,9,6,8,5
0,7,2,4,8,5,6,3,9
0,7,2,4,8,9,6,3,5
0,7,2,5,3,1,6,9,4
0,7,2,5,3,4,6,9,1
0,7,2,5,9,1,6,3,4
0,7,2,5,9,4,6,3,1
0,7,3,1,4,2,6,8,9
0,7,3,1,4,9,6,8,2
0,7,3,1,8,2,6,4,9
0,7,3,1,8,9,6,4,2
0,7,4,1,5,2,6,8,9
0,7,4,1,5,9,6,8,2
0,7,4,1,8,2,6,5,9
0,7,4,1,8,9,6,5,2
0,7,4,2,5,3,6,8,9
0,7,4,2,5,9,6,8,3
0,7,4,2,8,3,6,5,9
0,7,4,2,8,9,6,5,3
0,7,4,3,5,1,6,9,2
0,7,4,3,5,2,6,9,1
0,7,4,3,9,1,6,5,2
0,7,4,3,9,2,6,5,1
0,8,1,2,4,3,7,6,9
0,8,1,2,4,9,7,6,3
0,8,1,2,6,3,7,4,9
0,8,1,2,6,9,7,4,3
0,8,2,3,5,4,7,6,9
0,8,2,3,5,9,7,6,4
0,8,2,3,6,4,7,5,9
0,8,2,3,6,9,7,5,4
0,8,2,5,3,1,7,9,4
0,8,2,5,3,4,7,9,1
0,8,2,5,9,1,7,3,4
0,8,2,5,9,4,7,3,1
0,8,2,6,3,1,7,9,5
0,8,2,6,3,5,7,9,1
0,8,2,6,9,1,7,3,5
0,8,2,6,9,5,7,3,1
0,8,3,6,4,1,7,9,5
0,8,3,6,4,5,7,9,1
0,8,3,6,9,1,7,4,5
0,8,3,6,9,5,7,4,1
0,8,4,3,5,1,7,9,2
0,8,4,3,5,2,7,9,1
0,8,4,3,9,1,7,5,2
0,8,4,3,9,2,7,5,1
0,8,5,3,6,1,7,9,2
0,8,5,3,6,2,7,9,1
0,8,5,3,9,1,7,6,2
0,8,5,3,9,2,7,6,1
0,8,5,4,6,1,7,9,3
0,8,5,4,6,3,7,9,1
0,8,5,4,9,1,7,6,3
0,8,5,4,9,3,7,6,1
0,9,1,2,4,5,8,6,7
0,9,1,2,4,7,8,6,5
0,9,1,2,6,5,8,4,7
0,9,1,2,6,7,8,4,5
0,9,1,5,4,2,8,7,3
0,9,1,5,4,3,8,7,2
0,9,1,5,7,2,8,4,3
0,9,1,5,7,3,8,4,2
0,9,1,7,5,3,8,6,4
0,9,1,7,5,4,8,6,3
0,9,1,7,6,3,8,5,4
0,9,1,7,6,4,8,5,3
0,9,2,1,4,5,8,7,6
0,9,2,1,4,6,8,7,5
0,9,2,1,5,4,8,6,7
0,9,2,1,5,7,8,6,4
0,9,2,1,6,4,8,5,7
0,9,2,1,6,7,8,5,4
0,9,2,1,7,5,8,4,6
0,9,2,1,7,6,8,4,5
0,9,2,4,5,1,8,7,3
0,9,2,4,5,3,8,7,1
0,9,2,4,7,1,8,5,3
0,9,2,4,7,3,8,5,1
0,9,3,5,6,1,8,7,4
0,9,3,5,6,4,8,7,1
0,9,3,5,7,1,8,6,4
0,9,3,5,7,4,8,6,1
1,0,2,3,4,5,9,7,8
1,0,2,3,4,8,9,7,5
1,0,2,3,7,5,9,4,8
1,0,2,3,7,8,9,4,5
1,0,3,2,4,5,9,8,7
1,0,3,2,4,7,9,8,5
1,0,3,2,5,4,9,7,8
1,0,3,2,5,8,9,7,4
1,0,3,2,7,4,9,5,8
1,0,3,2,7,8,9,5,4
1,0,3,2,8,5,9,4,7
1,0,3,2,8,7,9,4,5
1,0,3,4,5,6,9,7,8
1,0,3,4,5,8,9,7,6
1,0,3,4,7,6,9,5,8
1,0,3,4,7,8,9,5,6
1,0,3,6,5,2,9,8,4
1,0,3,6,5,4,9,8,2
1,0,3,6,8,2,9,5,4
1,0,3,6,8,4,9,5,2
1,0,4,3,5,6,9,8,7
1,0,4,3,5,7,9,8,6
1,0,4,3,6,5,9,7,8
1,0,4,3,6,8,9,7,5
1,0,4,3,7,5,9,6,8
1,0,4,3,7,8,9,6,5
1,0,4,3,8,6,9,5,7
1,0,4,3,8,7,9,5,6
1,0,4,5,6,2,9,8,3
1,0,4,5,6,3,9,8,2
1,0,4,5,8,2,9,6,3
1,0,4,5,8,3,9,6,2
1,0,4,7,6,2,9,8,5
1,0,4,7,6,5,9,8,2
1,0,4,7,8,2,9,6,5
1,0,4,7,8,5,9,6,2
1,0,5,6,7,2,9,8,4
1,0,5,6,7,4,9,8,2
1,0,5,6,8,2,9,7,4
1,0,5,6,8,4,9,7,2

... in response to another 6th grader's home work assignment :)