Heres the question:

Two boys agree to mow a rectangular lawn 80m by 60m, each mowing half. The first boy mows a strip of uniform width around the outside of the lawn. how wide is the strip?

So far ive figured out that each boy mows half the area which is 2400m^2, and ive wrote out an equation of the area which is length=2400/width. Now im completely stuck, can someone please help me?