I need help a function relates an __value

Sadie computes the perimeter of a rectangle by adding the length, l, and width, w, and doubling this sum. eric computes the perimeter of a rectangle by doubling the length, l, doubling the width, w, and adding the doubled amounts. write an equation for sadie’s way of calculating the

What is best way to getting answer for my exam is

Rewrite so the subject can be y in the formula d=m-y/y+n