Opposite angles of a parallelogram are congruent.
Adjacent angles of a parallelogram are supplementary.
Set the measures of the two opposite angles equal and solve for x.
5x - 20 = 2x + 43
3x = 63
x = 21
Set the sum of two adjacent angles equal to 180.
5x - 20 + 4y - 5x = 180
-20 + 4y = 180
4y = 200
y = 50
