Algebra 1: Common Core (15th Edition)

Recall, the equation for the area of a rectangle is: $Area= length \times width$. We are told that the length is 5.5cm and that the area is 220 square cm, so we plug these numbers in to obtain: $220=5.5\times w$. We cancel out the multiplication by dividing both sides by 5.5 to obtain that w=40 cm.