Data Sufficiency

BTGmoderatorDC wrote: ↑

Sun Dec 05, 2021 7:20 pm

What is the value of x ?

(1) y - x = y - 6
(2) x + 2y = 10



OA A

Source: GMAT Prep

Target question: What is the value of x ?

Statement 1: y - x = y - 6
Note: In most cases, there are infinitely many solutions to a linear equation with two variables. However, in this case, one of the variables cancels, leaving us an equation with ONE variable
Subtract y from both sides of the equation to get: -x = -6
Multiply both sides of the equation by -1 to get: x = 6
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: x + 2y = 10
This case, none of the variables cancel, which means there are infinitely many solutions to the equation x + 2y = 10
Here are two possible solutions:
Case a: x = 0 and y = 5. In this case, the answer to the target question is x = 0
Case b: x = 10 and y = 0. In this case, the answer to the target question is x = 10
Since we can’t answer the target question with certainty, statement 2 is NOT SUFFICIENT

Answer: A

Cheers,
Brent