Answer:
a) 20 degrees
Explanation:
An isosceles triangle is a triangle that consists of two angles of equal size and one angle of different size. Along with this, all triangles have a total of 180 degrees.
For this problem, we can assume that the angle given is either the individual one or part of the pair. When it's a part of the pair, those two angles alone add up to 360, so it cannot be a part of the pair.
If the angle is the individual one, then the total of the other two angles would be 180-140, or 40. We can divide this by two to find the size of each angle individually, giving us 20 degrees. Thus, the only possible answer is a) 20 degrees.