If a length of a rectangle is four times its width. what is its perimeter is 90m. how can i find the dimentions

W = width
4w = length

perimeter = 2(length) + 2(width)
perimeter = 2(4w) + 2w
perimeter = 8w + 2w
perimeter = 10w
90 = 10w
9 = w

length = 4w, 4(9) = 36. 
 
Length is 36 m. Width is 9 m.

No he does not because he can only cover 12 square feet from 15 square feet which he will still need 3 more. this is because if 3×5=15 square feet and 15-12=3 which thats the answer