Eli and Samantha work at a dry cleaners ironing shirts. Eli can iron 20 shirts per hour, and Samantha can iron 35 shirts per hour. Samantha worked 2 more hours than Eli and they ironed 400 shirts between them. Write a system of equations that could be used to determine the number of hours Eli worked and the number of hours Samantha worked. Define the variables that you use to write the system.