Polynomial Division by Factoring

The total number of visitors who came to the Washington Theatre from May 1 to May 31 can be modeled by the function $F(x)=126x^3+279x^2+90x+450$ and the number of shows at the Washington Theatre from May 1 to May 31 can be modeled by $G(x)=18x+45$ where $x$ is the number of days since May 1. Which of the following expressions correctly describes the average number of visitors per show?