Answer
See graph.
\begin{cases} 2x+y\geq10\hspace2cm(protein) \\x+3y\geq15\hspace2cm(fat)\\x\geq0, y\geq0\end{cases}
Work Step by Step
Step 1. Assume the $x$ number of ounces of fish and $y$ number of ounces of beef byproducts are possible.
Step 2. Set up the inequalities based on the given conditions:
\begin{cases} 12x+6y\geq60\hspace2cm(protein) \\3x+9y\geq45\hspace2cm(fat)\\x\geq0, y\geq0\end{cases}
or
\begin{cases} 2x+y\geq10\hspace2cm(protein) \\x+3y\geq15\hspace2cm(fat)\\x\geq0, y\geq0\end{cases}
Step 3. We can graph the solution set as shown (solution region).
