Draw this out on a piece of paper if you can.
You know that a rectangle has the 2 lengths the same and the 2 widths the same.
draw the rectangle out and write 108 on each length (the long part not the short part)
You need to find what the width is (the short parts) so you substitute x in for both sides.
You now have a rectangle with 108 on 2 sides and x on the other 2 sides.
Make an equation that equals 756 square inches.
2x + 216 = 756
Subtract 216 from 756
2x = 540
x = 270
So the width of the roof is 270 inches wide.
