AD =77
1) In this trapezoid, since AD ≅ BC let's find the Diagonal, let's find x at first.
3x +20 = 5x -18
3x -5x = -20-18
-2x = -38
x= 19
Plugging x= 19 into any of those equations we have:
AD ≅ BC = 3(19)+20 = 77
BC =
2) Since the diagonals of a trapezoid are congruent to each other than. AD = 77