The sum of 1.5x and 16.5x is equal 180°.
1.5x + 16.5x = 180
18x = 180 |:18
x = 10
The angles 20y and 16.5x are the vertical angles, therefore:
20y = 16.5x
20y = 16.5(10)
20y = 165 |:20
y = 8.25
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