Data Sufficiency

Hi shibsriz,

This question looks like a "system" algebra question, so solving this with "math" is doable. As it stands, you CAN solve it by TESTing Values. Here's how:

We're told that 5A = 9B = 15C. We're asked for the value of A+B+C.

I'm always on the lookout for patterns in GMAT questions. Here, it's interesting that 5, 9 and 15 are used, since they're all multiples of the primes 3 and 5. That makes me wonder WHY....

Using that first equation, my thought is that we could use...
A=9
B=5
C=3

OR
A=0
B=0
C=0

Fact 1: 3C-A = 5C-3B

It's obvious that all 3 values could be 0, which would give us an answer of 0+0+0 = 0

Notice how the numbers here are ALSO multiples of 3 and 5???? Interesting.... It turns out that A=9, B=5 and C=3 also fits this equation...

3(3) - 9 = 5(3) - 3(5)
0 = 0

With these numbers, the answer to the question is 9+5+3 = 17
Fact 1 is INSUFFICIENT

Fact 2: 6BC = 10A

Here, we can also use "all 0s" and will get an answer of 0+0+0 = 0

A quick check of A=9, B=5 and C=3.....

6(5)(3) = 10(9)
90 = 90

Those same values fit this equation too; this gives us an answer of 9+5+3 = 17
Fact 2 is INSUFFICIENT

Combined, both sets of values fit both Facts (and the original equation), so we have 2 different answers.
Combined, INSUFFICIENT

Final Answer: E

GMAT assassins aren't born, they're made,
Rich