12. In the sum shown, different shapes represent different digits. What digit does the square represent?
A 2
B 4
C 6
D 8
E 9
12. C The maximum value one can obtain by adding a two-digit number and two one-digit numbers is $99+9+9=117$. Hence the triangle must represent 1 and therefore the sum of the three numbers is 111. To obtain this answer to the sum, the circle must represent 9 since $89+9+9$ is less than 111 . Hence the two squares must sum to $111-99=12$. Therefore the square represents the digit 6 .