The perimeter of a rectangle is 336 cm. The width is 20 cm. less than the length. What is the length?

1.) Plug the Perimeter and the width into the perimeter formula.
P= 2l + 2w

336= 2 (l) + (2) l - 20

2.) Distribute
336= 2l + 2l - 40

3.) Combine like terms
336= 4l - 40

4.) Add 40 to the other side
336 = 4l - 40
+40        +40

5.) Divide by 4
376= 4l
-----   ----
4         4

L= 94.