One number is 12 more than another. The sum of the smaller number and twice the larger number is 39. Find the larger number.
a) 5
b) 7
c) 17
d) 34
If a is large and b is small:
First rule: a = 12 + b
Second rule: b + 2a = 39
Solve those two equations for a. The answer is choice "c"