jmc

First we begin by solving the system of equations $$\begin{array}{rl}9s+5t& =108,\\ t-2& =s.\end{array}$$Making the substitution for $s$ from the second equation to the first, we get $9(t-2)+5t=108$, which simplifies to $14t-18=108$. Solving for $t$, we find that $t=\frac{108+18}{14}=\boxed{9}$.