Set 17: Systems of Equations

Choice C is correct. Choice C is the correct answer. We use substitution since $y = 4 x$ is already isolated. Step 1: Substitute $y = 4 x$ into $2x + y = 30$: $$$2x + (4 x) = 306x = 30$x = 5 Step 2: Find $y$ using $y = 4 x$: $y = 4(5) = 20$ Solution: $(5, 20)$ Verification: $2(5) + 20 = 10 + 20 = 30$ ✓ Strategic Tip: Substitution works best when one equation is already solved for a variable. Choice A is incorrect because $2(6) + 24 = 12 + 24 = 36 \neq 30$. Choice B is incorrect because $2(4) + 16 = 8 + 16 = 24 \neq 30$. Choice D is incorrect because $2(3) + 12 = 6 + 12 = 18 \neq 30$.