A fast way to solve this question? I solved it, but it took me more than 2 min :s.
What is the value of y^3 - t^3?
(1) y - t = 3
(2) y^2 - t^2 = 21
I spent a lot of time in solving the equations with the possible values of y and t.
(1) - (y-t) = 3 ----> Y & t can be anything -Insufficient
(2) (y+t)(y-t) = 3 x 7 ----> (y+t) can be 3 or 7 -----> i.e. y will be 5 for sure but t can be 2 or -2 ----> Insufficient
(1+2) (y+t)= 7 because (y-t) = 3----> y = 5 & t=2--->Sufficient
Hope it helps.
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