Problem 1
The exterior angles sum to 360
9v+(19v-21)+45+(v+48)+7v = 360
36v+72 = 360
36v+72-72 = 360-72
36v = 288
36v/36 = 288/36
v = 8
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Problem 2
Why is this? because TW is perpendicular to VS (the right angle marker shows this). At the same time, TW cuts VS into two equal pieces, ie VW = WS. The tickmarks indicate the segments are the same length.
