mketron wrote: Is ax = 3 - bx?
(1) x(a+b) = 3
(2) a = b = 1.5 and x = 1

Target question: Is ax = 3 - bx?
We can take the equation ax = 3 - bx, and rearrange the terms to get: ax + bx = 3.
So, let's rephrase the target question. . .

Rephrased target question: Is ax + bx = 3?

Statement 1: x(a+b) = 3
Expand this to get: ax + bx = 3
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: a = b = 1.5 and x = 1
Since we're given all three variables (a, b and x), we definitely have enough information to determine whether or not ax + bx = 3
So, statement 2 is SUFFICIENT

Answer = D

Cheers,
Brent

Hi mketron,

In DS questions, it's important to separate the QUESTION from the FACTS.

As a simple example...

Question: Is the car that I'm pointing at red?

Notice how that's just a question; we don't know if the car is red or not.

1) The car is red.

This FACT is enough information to answer the question, so Fact 1 is SUFFICIENT

Now, to this DS question....

Question: Is ax = 3 - bx?

We don't know anything about the variables a, b and x.

1) x(a + b) = 3

This FACT gives us an equation to work with. With some algebra, we get...

ax + bx = 3
ax = 3 - bx

We now KNOW that ax = 3 - bx, so this Fact is SUFFICIENT to answer the question.

The GMAT will throw a couple of DS questions at you in which the information needed to answer the question has been "rearranged" using math rules. Be prepared to play around with the facts and prove whether the info is sufficient or insufficient.

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