Question 577820
2 angles are complementary is their sum is 90 degrees, so:

a + b = 90

a + b/2 = 69             system of equations, multiply bottom by -1

a + b = 90
-a -b/2 = -69             add
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b - b/2 = 21
b/2 = 21
b = 21(2) = 42

a + 42 = 90
a = 90 - 42 = 48

Check:

a + b/2 = 69

48 + 42/2 = 69
48 + 21 = 69
69=69 √