IJKL is a rectangle, so opposite sides have the same length:
• IJ = KL ⇒ 6y - 6 = 2x + 20
• JK = IL ⇒ 3x + 21 = 6y
Substitute the second equation into the first and solve for x :
6y - 6 = 2x + 20
(3x + 21) - 6 = 2x + 20
3x + 15 = 2x + 20
x = 5
Solve for y :
3x + 21 = 6y
15 + 21 = 6y
36 = 6y
y = 6
