How do would you find the lengths of the parallel sides of a trapezoid when one side is 3 cm greater than the other side and has a height of 9 cm with an area of 40.5 square cm?

Let one side be x+3 and the other side be x:

1/2*(x+3+x)*9 = 40.5

Multiply both sides by 2:

(x+3+x)*9 = 81

9x+27+9x = 81

18x+27 = 81

Subtract 27 from both sides:

18x = 54

Divide both sides by 18:

x = 3

Therefore the parallels are 3 cm and 6 cm respectively.

Check: 1/2*(6+3)*9 = 40.5 square cm