Two rectangles have the same width. the length of one is 1 foot longer than the width. the length of the other is 2 feet longer than the width. the larger rectangle has 5 more square feet than the smaller. what is the width of the rectangles?

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?