if a and b are positive integers, what is the value of a + b?
1. a/b= 5/8
2. the greatest common divisor of a and b is 1.
I think the answer is C
From 1, a/b=5/8 a and b could be any 2 integers satisfying the ratio i.e. (5,8) or (10,16) etc
From 2, the GCD is 1 is INSUFF as a and b could be any 2 prime numbers
Combined, a=5 and b=8 are the only values possible hence a+b = 13