Question: What is the value of x+3y+7?
(1) X - 3Y = 0
(2) X^2 + 4Y^2=0
Statement 1 is not sufficient, since while we can work out that x = 3y, which means we're trying to work out the value of 6y + 7, we don't have any information about the value of y. It might be that x = y = 0, in which case x + 3y + 7 = 7, or it might be that x = 3 and y = 1, in which case x + 3y + 7 = 13, among many other possibilities.
From Statement 2, since x^2 and y^2 are both squares, they can never be negative; each must be at least zero. The only way for x^2 + 4y^2 = 0 to be true then is if x^2 and y^2 are both zero, in which case x = 0 and y = 0. So Statement 2 is sufficient, and the answer is B.
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