# Chapter 2 - Section 2.1 - The Parallel Postulate and Special Angles - Exercises - Page 74: 1b

m$\angle$7 = 72$^{\circ}$

#### Work Step by Step

m$\angle$1 = 108$^{\circ}$ By the Corresponding Angles Postulate: m$\angle$1 = m$\angle$5 By the Linear Pair Postulate: m$\angle$5 + m$\angle$7 = 180$^{\circ}$ Substitute the value of 108 into the equation. 108 + m$\angle$7 = 180 Subtract 108 from both sides 108 - 108 + m$\angle$7 = 180 - 108 Simplify. m$\angle$7 = 72$^{\circ}$

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