In a parallelogram, opposite sides are equal.
ON = LM
OL = NM
OL = y-6
NM= 1/3 x
ON= 5x-8
LM= 9x-26
First, solve for x
ON = LM
5x - 8 = 9x - 26
-8 + 26 = 9x - 5x
18 = 4x
18/4 = x
x = 4.5
Replace x=4.5 on NM, and solve for y:
OL = NM
y-6= 1/3x
y-6 = 1/3 (4.5)
y-6= 1.5
y= 1.5 + 6
y= 7.5 = 15/2