Choice C is the correct answer. Let $c$ be cookies and $b$ be brownies.

System: $\begin{cases} c + b = 50 \\ 2c + 3b = 120 \end{cases}$

Step 1: I 💡 Strategic Tip: Word problems with totals naturally lead to systems of equations.

Choice A is incorrect because$2(25) + 3(25) = 125 \ eq 120$.

Choice B is incorrect because$2(35) + 3(15) = 115 \ eq 120$.

Choice D is incorrect because$2(20) + 3(30) = 130 \ eq 120$.