Step 1 :Determine the limits of integration for the $x$ and $y$ variables over the triangular region
Step 2 :Split the region into two parts: the first part bounded by $y=0$, $y=x$, and $x=12$, and the second part bounded by $y=0$, $y=24-x$, and $x=12$
Step 3 :For the first part, set the limits of integration for $y$ from $0$ to $x$, and for $x$ from $0$ to $12$
Step 4 :For the second part, set the limits of integration for $y$ from $0$ to $24-x$, and for $x$ from $12$ to $24$
Step 5 :Write the single iterated integral for the entire region as the sum of the integrals for the two parts: \(\int_{0}^{12} \int_{0}^{x} f(x,y) \, dy \, dx + \int_{12}^{24} \int_{0}^{24-x} f(x,y) \, dy \, dx\)
Step 6 :\(\boxed{\int_{0}^{12} \int_{0}^{x} f(x,y) \, dy \, dx + \int_{12}^{24} \int_{0}^{24-x} f(x,y) \, dy \, dx}\)