Question

Area of room is 320 and width is 4/5 of length

Answer 1

Area is w*l and
`w=\frac{4l}5`, thus the area is
`\frac{4l^2}5`. Make it equal to 320 and you get
`l^2=400`, thus
`l=\pm{20}`, the minus one not being meaningful in our context. Thus the length is 20, while the width is 16.