In triangle ABC, ∠A=20∘ and ∠B=80∘. Let D be a point on line segment AB such that AD=BC. What is the measure (in degrees) of ∠ADC?

Answer 1

See:

http://www.jiskha.com/display.cgi?id=1373027638

Answer 2

150

Answer 3

That's true, it should be the supplement of asin()=180-31.6=148 (nearest degree).