an equation you could use to find the length would be 2x+5. The width would be x. In order to find the perimeter:
2(2x+5) + 2(x)=88
4x+10+2x=88
6x+10=88
6x=78
x=13
The width is 13 since it is x and if we plug 13 into the equation 2x+5, the length would be 31.