Parallelogram has opposite sides congruent. i.e. of equal length. So, you have these equations: 1) |AB| = |CD|, or 3y - 6 = 2y + 4. The solution is 3y - 2y = 4 + 6, or y = 10. and 2) |BC| = |AD|, or 5x-8 = 4x - 1. The solution is 5x - 4x = 1 + 8, or x = 9.