A company that teaches self-improvement seminars is holding one of its seminars in Oakland. The company pays a flat fee of $300 to rent a facility in which to hold each session. Additionally, for every attendee who registers, the company must spend $20 to purchase books and supplies. Each attendee will pay $80 for the seminar. Once a certain number of attendee register, the company will be breaking even. How many attendees will that take?

Let's denote the number of attendees as "x".

The company incurs a cost of $300 to rent the facility and an additional cost of $20 for each attendee to purchase books and supplies. Therefore, the total cost for the company is given by:
Cost = $300 + $20x

Each attendee pays $80 for the seminar. Therefore, the total revenue for the company is given by:
Revenue = $80x

The company will break even when the total cost equals the total revenue:
Cost = Revenue

So, we can write the equation:
$300 + $20x = $80x

Simplifying the equation, we get:
$300 = $60x

Dividing both sides by $60, we get:
5 = x

Therefore, the company will break even when 5 attendees register.