Quadrilateral ABCD is inscribed in this circle.
What is the measure of angle B?
Opposite angles in a cyclic quadrilateral are supplementary....so....
x + 4x - 20 = 180 add 20 to each side
5x = 200 divide both sides by 5
x = 40°
So....angle B = (4(40) - 20) = 160 - 20 = 140°
