Question

Solve for x. A. 6 B. 8 C. 12 D. 18

Answer 1

Since the horizontal lines are parallel, we know from similar figures that the ratios are proportional.
when
24/x=36/12, or 

24    36
--   = ---
x      12

We divide the product of diagonals with numbers (24*12) by the number across from x (36) to get the value of x, i.e.
x=(24*12)/36=288/36=8