Leah and Christopher work at a dry cleaners ironing shirts. Leah can iron 25 shirts per hour, and Christopher can iron 15 shirts per hour. Leah and Christopher worked a combined 13 hours and ironed 265 shirts. Write a system of equations that could be used to determine the number of hours Leah worked and the number of hours Christopher worked. Define the variables that you use to write the system.
L+C = 13
25L + 15C = 265