Question

An artist intends to paint a 60-square-foot mural on a large wall that is 18 ft wide and 11 ft tall. find the dimensions of the mural if the artist leaves a border of uniform width around it.

what formula do I use please?

Answer 1

taking off the width of w from each of the four sides, we have
(18-2w)(11-2w) = 60
now just wind w

or, look for two factors of 60 which differ by 7
5*12 = 60
...