For a parallelogram, 3y+8 = 2x-4 and 5y = x+8
This is because the parallel sides are equal
3y + 8 = 2x-4 ..........(1)
5y = x+8...............(2)
from equation 2, y =(x+8)/5 .......(3)
substituting for y in equation (1) we have
3(x+8)/5 + 8 = 2x -4
3x+24 +(5x8) =5(2x-4)
3x+24 + 40 = 10x - 20
10x -3x = 40 +24+20
7x = 84
x = 12
From (2) , substituting for x yields
5y = x+8
5y = 12 +8
5y =20
y = 4