A hotel 35 miles from an airport runs a shuttle service to and from the airport. The 9:00 A.M. bus leaves for the airport traveling at 30 miles per hour. The 9:15 A.M. bus leaves for the airport traveling at 40 miles per hour. Write a system of linear equations that represents distance as a function of time for each bus. Graph and solve the system. How far from the airport will the 9:15 A.M. bus catch up to the 9:00 A.M. bus?

Okay I kind of understand the problem, but I just don't get how to set up a system of linear equations. From the application problem, I can only think of one. Help?

BTW, I'll graph the system of equations myself. I also attached a picture of the problem for reference.