Most Test Takers would probably solve this problem using Algebra, as substituting in the given values is a fairly straight-forward bit of 'math.' This question can also be solved by TESTing VALUES...
We're told that....
X = (K)(C)
Y = (K)(T)
We're asked for the value of Y-X...
K = 1
C = 2
T = 3
X = (1)(2) = 2
Y = (1)(3) = 3
Y-X = 3-2 = 1
Answer A: K(T-C) = 1(3-2) = 1 This IS a MATCH
Answer B: K(C-T) = 1(2-3) = -1 NOT a match
Answer C: C(K-T) = 2(1-3) = -4 NOT a match
Answer D: T(K-C) = 3(1-2) = -3 NOT a match
Answer E: K(1-T) = 1(1-3) = -2 NOT a match
GMAT assassins aren't born, they're made,
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