## Thinking Mathematically (6th Edition)

$m\angle{1} = 110^o \\m\angle{2} = 70^o \\m\angle{3} = 110^o$
RECALL: (1) Vertical angles have equal measurements. (2) Supplementary angles have a sum of 180 degrees. The 70-degree angle and angle 2 are vertical angles, so they have the same measurement. Thus, $m\angle{2} = 70^o$. Angles 1 and 2 are supplementary, so their sum is 180 degrees. Thus, $m\angle{1}= 180^o- m\angle{2}=(180-70)^o=110^o$ Angles 1 and 3 are vertical angles, so they have equal measurements. Thus, $m\angle{3} = 110^o$.