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Bunuel
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Your reasoning is correct for the whole problem. I'd like to point out that X cannot be -2 in your counter example, though, as we are given x > w and w = 2. More appropriate counter examples would be x = 5, y = 7 -> avg = 8 > y = 7; also y cannot equal 20 as y < z = 18. Again, a more appropriate counter example might be x = 3 and y = 17 -> avg = 10 < y = 17.
Fdambro294
Is: (W + X + Y + Z) / 4 > Y?

Is: W + X + Y + Z > 4Y?

Is: W + X + Z > 3Y?

Given: W < X < Y < Z


S1: W + Z = X + Y

W = X + Y - Z

Inserting S1 into the question stem


Is: (X + Y - Z) + X + Z > 3Y?

Is: 2X + Y > 3Y?

Is: X > Y?

We are given that X < Y

Definite answer: s1 sufficient alone.


S2: again plug in the given values into the question stem.

Question becomes:

Is: 20 + X > 3Y?

Even given the constraint that X < Y, you can easily find two cases that give you a Yes and No.

If X = -2 and Y = 1 ——-Yes

If X = 2 and Y = 20 ——- NO


A
S1 alone is sufficient

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