Bridgette is going to the water slides and needs to figure out which deal is better. She can pay $30 to go on the water slides as much as she wants, or she can pay $15 to get in, plus an additional $3 per trip down the water slides. If Bridgette goes on a certain number of trips down the water slides, the two options are equivalent in terms of cost. How many trips is that? Write a system of equations, graph them, and type the solution.