body{margin:0;} noscript{z-index: 10000; position: fixed; display: block; height: 100%; width: 100%; background: #fff;} noscript .fa{font-size: 40px; display:block; color: #daa520;} noscript div{margin-top: 6%; padding-left: 20px; padding-right: 20px; text-align: center;} ! You must have JavaScript enabled to use this site.

Big Ideas Math: Modeling Real Life, Grade 7

BI

Big Ideas Math: Modeling Real Life, Grade 7 View details

5. Finding Unknown Angle Measures

Continue to next subchapter

Exercise 25 Page 395

If the angles in the diagram make up a straight line, we know that they are supplementary.

Classification: Supplementary angles.
Value of x: 20

Practice makes perfect

First, let's take a look at the given diagram.

Because the angles in the diagram make up a straight line, we know that they are supplementary. Since the angles are supplementary, we know that the sum of their measures should equal 180^(∘). We can solve for x by creating an equation using the expressions for the two smaller angles and their sum.

7x^(∘) + (x+20)^(∘) = 180^(∘)

Add terms

8x^(∘) + 20^(∘) = 180^(∘)

LHS-20^(∘)=RHS-20^(∘)

8x^(∘) = 160^(∘)

.LHS /8.=.RHS /8.

x^(∘) = 20^(∘)

Subchapter links

Try It p.390-392

Self-Assessment for Concept & Skills p.392

Self-Assessment for Problem Solving p.393

Review & Refresh p.394

Concept, Skills, & Problem Solving p.394-396