In trapezoid ABCD, sides AB and CD are parallel, angle A = 2(angle D), and angle C = 3(angle B). Find angle B
Since AB is parallel to CD....then BC is a transversal cutting two parallel lines
So.....angles B and C are supplementary [sum to 180° ]
So
B + C = 180
B + 3B = 180
4B = 180
B = 45°
+188 
