Answer:
x = 35
Explanation:
Complementary angles refers to a pair of angles which add up to make a 90° right angle.
Lets assume them as Angle A And Angle B.
Angles A = 40°
Angles B = x+15
Angle A + Angle B = 90°
40+15+x = 90°
x = 90 - 55
x = 35°
So, x = 35°