w - width
3w - 1 - length
54 in - perimeter
w + w + (3w - 1) + (3w - 1) = 8w - 2 - perimeter
The equation:
8w - 2 = 54 <em>add 2 to both sides</em>
8w = 56 <em>divide both sides by 8</em>
w = 7
3w - 1 = 3(7) - 1 = 21 - 1 = 20
