Angle C of an isosceles trapezoid ABCD is 40 degrees greater than angle A. Find the degree measure of angle B.

Let the value of the angle ВAD = X0, then, by condition, the angle ВAD = (X + 40) 0.
Since the sum of the angles at the side of the trapezoid is 180, the angle ABC = (180 – X) 0, and the angle СDA = (180 – X – 40) = (140 – X) 0.
Since the trapezium is isosceles, the angle ВAD = СDВ, and the angle ABC = ВСD.
X = (140 – X).
2 * X = 140.
X = 140/2 = 70.
Then the angle ABC = ВСD = 180 – 70 = 110.
Answer: The degree measure of the angle ABC is 110.