Write a system of equations to describe the situation below, solve using substitution, and fill
in the blanks.
Quincy is going to the water slides and needs to figure out which deal is better. He can pay
$30 to go on the water slides as much as he wants, or he can pay $18 to get in, plus an
additional $2 per trip down the water slides. If Quincy 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?
What is the cost?