Question: how do you find the height of a rectangle if you know the length and width?
Answer: For example, if a rectangle has an area of 20 square feet and a length of 10 feet, divide 20 by 10 to get a width of 2 feet. Multiply the length times 2 and subtract this figure from the perimeter, if you're given these values. Then divide by 2 to find the width.