16. x = 25 , each angle = 65°
angle (3x - 10) and (x + 40) are complementary angles and thus equal
3x - 10 = x + 40
subtract x from both sides
3x - x - 10 = 40
2x - 10 = 40
add 10 to each side
2x = 40 + 10 = 50 ⇒ x = 25
3x - 10 = (3 × 25) - 10 = 65°
x + 40 = 25 + 40 = 65°