The area of a rectangle is 36 square feet. find the length and width if the length is 4 times the width

Area of a rectangle= length x width

length= 4 x width

36= width x (4 x width)

36= 4 x width^2

36/4= width^2

9=width^2

square root (9)= width

width= 3

36=length x width

36= length x 3

36/3= length

length=12