At a local movie theatre, sodas cost $4.50 and bags of popcorn cost $1.50. Kirk buys three times as many bags of popcorn as sodas and pays a total of $36. (a) If s is the number of sodas bought and p is the number of bags of popcorn, write a system of equations that models this scenario and explain how your system models the problem.
(b) Determine how many of each item Kirk bought. Do this by using an algebraic solution to the system you wrote in (a).