math
posted by ALICIA .
AB+CD=AAA
What is the value of C?
Choices: 1, 3, 7, 9, or N/A

Easier if you write it as
_AB
_CD+
____
AAA
The largest A+C can be is 18 (1 carried plus say A or C=9 and A or C=8) so A must =1 (it can't=0)
rewrite
_1B
_CD+
____
111
In order for 1+C=11, C =9 with 1 carried from B+D.
We don't need to know what B and D are.