Set 13: Systems of Equations (Advanced)

Choice B is correct. Choice B is the correct answer. Let $s$ be the cost of a small drink and $L$ be the cost of a large drink. Given: $s = 4$ and $3s + 2 L = 18$ Step 1: Substitute $s = 4$: 3(4) + 2 L = 18$12+ 2 L = 18$$$ Step 2: Solve for $L$: $$$2L = 6$L = 3 Solution: One large drink costs $$3$. Verification: $3(4) + 2(3) = 12 + 6 = 18$ ✓ Strategic Tip: When one variable is given, substitute it immediately to reduce the problem to a single equation. Choice A is incorrect because $3(4) + 2(2) = 12 + 4 = 16 \neq 18$. Choice C is incorrect because $3(4) + 2(4) = 12 + 8 = 20 \neq 18$. Choice D is incorrect because $3(4) + 2(5) = 12 + 10 = 22 \neq 18$.