Oof this is probably really simple to most of y'all but I'm out of it.
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Answers:
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Explanation:
The two angles form a straight line, which is 180 degrees
Add up the angle expressions and set the sum equal to 180.
(angle1) + (angle2) = 180
(4x) + (x-15) = 180
(4x+x)-15 = 180
5x-15 = 180
5x = 180+15
5x = 195
x = 195/5
x = 39
We use that x value to find each missing angle
Then notice how angle1+angle2 = 156+24 = 180 to verify the answer.
Side note: Angles that add to 180 are considered supplementary.