In a parallelogram, opposite sides have the same length.
3x + 9 = 5x -5
group like terms on one side
9 + 5 = 5x -3x
14 = 2x
x is 7.
Since AB is 5x -5
AB = 5(7) -5
AB = 30.
BX is half of the line DB. So BX = DX
5y = 7y - 10
10 = 7y -5y
10 = 2y
y =5.
Since BX = 7y - 10
BX = 7(5) -10
BX = 25