The length of a rectangle is one unit shorter than one-sixth of the width, x.

Which expression represents the perimeter of the rectangle?

To answer this question, you need to know the formula for calculating the perimeter of a rectangle and translating the description into the formula. The description formula should be:

width = x

length - 1 = 1/6 x

length = 1/6 x + 1

Then adding them to perimeter formula you will get

perimeter = length * width

perimeter = 1/6x + 1 * x = 1/6x^2 + x