Given x = y + z. Is x > y ? (1) y > 0 (2) z > 0

Great question!

Given: Given x = y + z

Target question: Is x > y ?
This is a good candidate for rephrasing the target question.

Aside: the video below has tips on rephrasing the target question

Take x > y, and subtract y from both sides to get: x - y > 0
So, asking Is x > y? is the SAME AS asking Is x - y > 0?

REPHRASED target question: Is x - y >?

Statement 1: y > 0
There are several values of x, y and z that satisfy statement 1. Here are two:
Case a: x = 3, y = 2 and z = 1 (this satisfies the given condition that x = y + z. In this case, x - y = 3 - 2 = 1. So, the answer to the REPHRASED target question is YES, x - y IS greater than 0
Case b: x = 2, y = 3 and z = -1 (this satisfies the given condition that x = y + z. In this case, x - y = 2 - 3 = -1. So, the answer to the REPHRASED target question is NO, x - y is NOT greater than 0
Since we cannot answer the REPHRASED target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: z > 0
It's given that x = y + z
This means that x - y = z
Since statement 1 tells us that z > 0, then it is the case that x - y > 0
PERFECT!!
The answer to the REPHRASED target question is YES, x - y IS greater than 0
Since we can answer the REPHRASED target question with certainty, statement 2 is SUFFICIENT

Answer: B

Cheers,
Brent

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