Pearson Geometry Common Core, 2011
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Pearson Geometry Common Core, 2011 View details
Chapter Review
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Exercise 25 Page 73

The sum of measures of labeled angles is equal to 90^(∘).

x=15

Practice makes perfect
We have been asked to find x. We can see that the unknown angles on the figure are complementary, because their sum is the angle marked with a square — a right angle.
The sum of measures of two complementary angles is equal to 90^(∘). Let's write this fact as an equation and solve for x.
(3x)+(4x-15)=90
Solve for x
3x+4x-15=90
7x-15=90
7x=105
x=15