Interior angles of pentagon equals 540°. So if we add up all the angles, the result should be 540°. The upper angles are right angle so each of them is 90°
Put the numbers ∠1 + ∠2 + ∠3 + ∠4 + ∠5 = 540° x + 150° + 150° + 90° + 90° = 540° x + 480° = 540° x = 540° - 480° x = 60°
