Width= 71ft
Length=91ft
In this case you are given the rectangular area ( 6,461 square feet) and the length to width relation (length= width +20 ft). Since area is length multiplied by width, then the equation would be:
Area= length x width
Area= (width+20ft) x width
width^2 + 20width - 6461 =0
(width+91 ) (width-71)
Then width should be either 71 ftor (-91)ft. Since width is not possible minus, it definitely 71ft. Then length would be
Length= width+20= 71 +20= 91ft
