Below are two parallel lines with a third line intersecting them.
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Answer:
360 degrees around a point. the angle opposite 125 is vertically opposite so will be 125. 125 X 2 = 250
360 - 250 = 110. 110/2 = 55 degrees.
the angle opposite X is vertically opposite and is also an alternate angle to the angle of 55 degrees.
X = 55 degrees