If those are angles then they must be equal as one of the conditions of a parallelogram.
5x - 1 = 2x + 5 Add 1 to both sides
5x = 2x + 5 + 1
5x = 2x + 6 Subtract 2x from both sides.
5x - 2x = 6
3x = 6 Divide by 3
x = 6/3
x = 2
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