Given: 2x + y = 7
Target question: What is the value of x ?
Statement 1: y = 3
Substitute into the given equation to get: 2x + (3) = 7
Solve to get x = 2
Since we can answer the target question with certainty, statement 1 is SUFFICIENT
Statement 2: 3x + y = 9
We can rewrite this equation as follows: x + (2x + y) = 9
Since the given information tells us that 2x + y = 7, we can take x + (2x + y) = 9 and substitute to get: x + 7 = 9
Solve to get x = 2
Since we can answer the target question with certainty, statement 2 is SUFFICIENT
Answer: D
Cheers,
Brent
