First, you want to establish your equations.
L=7W-2
P=60
This is what we already know. To find the width, we have to plug in what we know into P=2(L+W), our equation to find perimeter.
60=2(7W-2+W)
Now that we only have 1 variable, we can solve.
First, distribute the 2.
60=14W-4+2W
Next, combine like terms.
60=16W-4
Then, add four to both sides.
64=16W
Lastly, divide both sides by 16
W=4
To find the length, we plug in our width.
7W-2
7(4)-2
28-2
L=26