Plugging values is another method, you can use to solve this one!

Let a=3, b=2, x = 3+2 = 5

Similarly y = 3-2 = 1

We know that 3ab = 3*2*3 = 18

Of the answer options,

A. (3x^2 - 3y^2)/4 = 3(25) - 3(1)/4 = 75 - 3/4 = 18B. (3y^2 - 3x^2)/4 = 3(1) - 3(25)/4 = 3 - 75/4 = -18

C. 3x+3y/2 = 3(5) + 3(1)/2 = 9

D. 3x - 3y/2 = 3(5) - 3(1)/2 = 6

E. 3x^2 - 3y^2/2 = 3(25) - 3(1)/2 = 73 - 3/2 = 36

Hence, Option A is the answer.

If you started with evaluating the first choice, it wouldn't take much time to find the answer.

_________________

You've got what it takes, but it will take everything you've got