A phone company offers two monthly plans. Plan A costs $14 plus an additional $0.15 for each minute of calls. Plan B costs $25 plus an additional $0.13 for each minute of calls.
For what amount of calling do the two plans cost the same?

What is the cost when the two plans cost the same?

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?