D. 62 because if we separate the shape into two then one will be 5*4 and the other will be 7*6. Adding them up will equal the whole shape.
Isolate one term (x or y) in one of the equations
6x+6y=0
6x=-6y
X= -1y
Substitute x=-y into the other equation
-7(-y) + 2y =18
7y + 2y =18
9y=18
Y=2
Substitute y=2 into 6x+6y=0
6x + 6(2) = 0
6x + 12=0
6x= -12
X = -2
So basically you just need to do the Pythagorean theorem to find the sides of the shaded rectangle, with c being the length of the side.
Small side:
2^2 + 6^2 = c^2
4 + 36 = c^2
40 = c^2
C is similar to 6.32456
Long side:
12^2 + 4^2 = c^2
144 + 16 = c^2
160=c^2
C is similar to 12.64911
And then you just multiply!