Part 1
p=2(l+w) is the formula for the perimeter of a rectangle (like a yard). I want to put a fence around the perimeter of the yard where we're buying our house (next week). I know the fencing costs $3 per foot.
Give me a formula for the cost of the fence in terms of the length (l) and the width (w). I want to be able to just plug in l and w as soon I get a change to measure the fence and then be able to calculate the cost.

Question

Part 1
p=2(l+w) is the formula for the perimeter of a rectangle (like a yard). I want to put a fence around the perimeter of the yard where we're buying our house (next week). I know the fencing costs $3 per foot.
 Give me a formula for the cost of the fence in terms of the length (l) and the width (w). I want to be able to just plug in l and w as soon I get a change to measure the fence and then be able to calculate the cost.