The length is equal to 7.
The width is equal to 3.
l = 1 + 2w
2l + 2w = 20
Since we have a value for l, we can plug it into the second equation.
2(1 + 2w) + 2w = 20
Distributive property.
2 + 4w + 2w = 20
Combine like terms.
2 + 6w = 20
Subtract 2 from both sides.
6w = 18
Divide both sides by 6.
w = 3
Now that we have a value of w, we can plug it into the original equation to find the exact value of l.
l = 1 + 2(3)
l = 7