Becky is a kickboxing instructor who will be teaching classes at a local gym. To get certified as an instructor, she spent a total of $90. Becky will be earning a base salary of $50 per month from the gym, plus an additional $5 for every class she teaches. If Becky teaches a certain number of classes during her first month as an instructor, she will earn back the amount she spent on certification. How many classes will that take? Write a system of equations, graph them, and type the solution.