X=120
This is the answer because 120-21=99
a. Use the inclusion/exclusion principle.

b. By definition of conditional probability,

A line. It goes in both directions forever
Sum of all adjacent angles is 180°.
3x + 12 + x = 180
4x + 12 = 180
4x = 168
x = 42°
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Answer: x = 42°
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The answer will be 2(x+3)