Applications of Rational Expressions and Word Problems

Dexter and Marley live far away, although still within driving distance. It takes Dexter $3$ hours to drive to Marley's. It takes Marley $2.5$ hours to drive.

$$\\$$

There is a theme park roughly at the midpoint between Dexter and Marley. They decide to meet there at the same time. Who needs to leave their home earlier, by how much?