The 8th puzzle is not solvable: Due to the numbers 1-9 having either 3,4 or 5 letters in their name, in the first row, you would need to use 4 at least twice, one of them beeing in the top right corner and also due to a multiple of an even number always beeing even, the bottom right corner also has to be even, which contradicts the contition of the right column only having 1 even Number.
@Matthew: But if the second digit has to be even and the numbers 1-9 only have 3,4 or 5 letters, the second digit HAS to be a 4... (i double checked the english spellings)
@Melli: the second digit doesn't need to be even, only the final digit of the second column must be even (the column contains a three digit even number). I'm going to add a clarification to make this clearer.
on /blog/58