We'll use x for the unknown. This is the equation you would use. The width is x and the length is 2x + 4. Here is the equation:
2(2x + 4) + 2x = 86
Distribute:
4x + 8 + 2x = 86
Simplify:
6x + 8 = 86
Subtract:
6x = 78
Divide:
x = 13
The length is 30 and the width is 13
Hope this helps!! :)