You are building a rectangular dog pen with an area of 90 ft^2. you want th length of the pen to be 3ft longer than twice the width. which equation can you use to find the width w of the pen?

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?