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Big Ideas Math: Modeling Real Life, Grade 7

BI

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

5. Finding Unknown Angle Measures

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Exercise 28 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: 31

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.

(3x+25)^(∘) + 2x^(∘) = 180^(∘)

Add terms

5x^(∘) + 25^(∘) = 180^(∘)

LHS-25^(∘)=RHS-25^(∘)

5x^(∘) = 155^(∘)

.LHS /5.=.RHS /5.

x^(∘) = 31^(∘)

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