Question

Suppose you know that ∠S and ∠Y are complementary, and that m∠S = 2(m∠Y) − 45°. Find m∠Y.

Answer 1

If S and Y are complementary, that means they add to 90.

So S + Y = 90
And S = 2Y - 45

Use substitution to plug 2Y - 45 in for S.

(2Y - 45) + Y = 90

3Y - 45 = 90
3Y = 135
Y = 45

If Y equals 45, then S also equals 45 since S+Y=90.