Write a system of equations to describe the situation below, solve using any method, and fill in the blanks.
A company that teaches self-improvement seminars is holding one of its seminars in Sparrowtown. The company pays a flat fee of $120 to rent a facility in which to hold each session. Additionally, for every attendee who registers, the company must spend $3 to purchase books and supplies. Each attendee will pay $15 for the seminar. Once a certain number of attendees register, the company will be breaking even. How many attendees will that take? What will be the company's total expenses and revenues?
Once___ attendees have registered, the company's expenses and receipts will both total $___.