Question 779649
Complementary angles have a sum of 90°

let x = measure of an angle
    90-x = measure of its complement

x = (90-x) + 10
x = 100 - x
x + x = 100
2x = 100
2x/2 = 100/2 (divide both sides by 2 to isolate x) 
x = 50° (MEASURE OF FIRST ANGLE)

90-x = ?
90-50 = 40° (substitute value of x which is 50 to get the COMPLEMENTARY ANGLE)

50° + 40° = 90°