Write and solve an equation (or a system of equations) for the situation below. Define your variables and write your solution as a sentence. Homework Help ✎

Kelly and Jack participated in a cross-country bicycle race sponsored by the school. They left school at the same time and rode their bikes on the same path. If Kelly traveled 15 kilometers per hour and Jack traveled 12 kilometers per hour, how long does it take for Kelly to be 18 kilometers ahead of Jack on the path?