Arectangle has an area of 4 square meters. the width is
1/5 meter. what is the length of the rectangle?

Given:
Area of a rectangle = 4 square meters
wight = 1/5 meter

find the length

Area of a rectangle = length * width

length = area / width
length = 4 m² ÷ 1/5 m
length = 4 m² * 5/1m 
length = 20 m

length is 20 meters.

Area = 20 m * 1/5 m = 20 m² / 5 = 4m²

What’s the equation you are trying to solve to get x?