36)
Triangle WVX is similar to triangle WZY. If two traingles are similar, it means that the ratio of their corresponding sides is equal. This means that
WV/WZ = VX/ZY = WX/WY
From the information given,
WX = 7, WY = a, WV = 6, VZ = a - 9
WZ = WV + VZ = 6 + a - 9 = a - 3
Thus, we have
6/(a - 3) = 7/a
By crossmultiplying, it becomes
6 x a = 7(a - 3)
6a = 7a - 21
7a - 6a = 21
a = 21
Since WY = a, then
WY = 21
