Answer of no. 2
We know that in a trapezium, side AB is parallel to side DC,
So, angle A and angle D are complimentary......that is they add up to 180 degrees
Also angle B and angle C are complimentary (just for your understanding)
angle A = x degrees
angle D = (3x - 20) degrees
Therefore :
x + 3x - 20 = 180
4x = 160
x = 40 degrees