Hey!
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Question #1:
Both triangles are the same because each one as a 90 degree angle and the quarter circle in both triangles means they both have another similar angle.
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Question #2:
You are correct!
The purpose of (x + 68) is to understand what L2's angle is. So 68 plus a number equals 180. In this case it would be 180 - 68 = 112.
L1 = 68°
L2 = 112°
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Hope This Helped! Good Luck!