Opposite sides of a parallelogram are equal lengths, so ...
... AB = CD
... 6x +30 = 2y -10
and
... BC = AD
... 2x -5 = y -35
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The equations can be put in standard form to get
... 3x -y = -20
... 2x -y = -30
Subtracting the second from the first, we get
... x = 10
Solving for y, we have
... y = 2x+30 = 2·10 +30 = 50
The values of x and y are x=10, y=50.
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AB = 6x+30 = 90
BC = 2x-5 = 15
