CE and DE are perpendicular, so the angle they share, x, is a right angle. Since the interior angles of a triangle are supplementary, the other two angles in the triangle must be complementary. We know that the bottom-left angle of the triangle is one of two supplementary angles, because it sits on a straight line with the other angle, which measures at 132°. If we subtract 132 from 180, we get 48, so the bottom left angle is 48°. Since the final angle of the triangle is complementary with that angle, it measures at 42° because 90 - 48 = 42. Angle B and this angle are supplementary, as they sit on a line together, so 180 - 42 = 138, thus angle B = 138°
x° = 90°
B° = 138°