Re: GRE Math Challenge #132- x + y + n = 15 x + y + k = 9
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28 Sep 2020, 08:57
When a question asks us to find the value of (n-k), we try to find the value of (n-k) by manipulating the equations. Trying to find n and k separately and then finding n-k is a very common trap that one can get into. If you thought like this, you were probably wondering how you could find out the values of n and k when there are fewer equations than unknowns.
x+y+n = 15
x+y+k = 9.
Subtracting the second equation from the first, we have n-k = 6.
So, there is no need to find out n and k to compute n-k.
Quantity A is equal to Quantity B.
Correct answer is option C.