Is it possible for a trapezoid to have 3 right angles

No, because if a trapezoid were to have three right angles, the fourth angle would also be right, because the angles of a quadrilateral add up to 360, and a quadrilateral with four right angles is a rectangle, which has two sets of parallel sides instead of one set like a trapezoid does.

No, this is because if a trapezoid has 3 right angles, the fourth and last one would also have to be a right angle and it is supposed to be an acute angle. To make it less confusing, a right angle is is in the shape of a "L" and if it had three "L’s" it would have to have another one too which would then make it a rectangle. !