Set 5: Linear Inequalities

Choice A is correct. Choice A is the correct answer. Environmental constraint problems require setting up inequalities based on targets. 1. Current situation: 680 tons currently 2. Target: After reduction, must be $\leq 500$ tons 3. Set up: $680- r \leq 500$ (current minus reduction) 4. Solve: Subtract 680: $-r \leq -180$, then divide by -1: $r \geq 180$ Strategic Tip: "Minimum reduction" means the reduction must be at least that amount, translating to $\geq$. Choice B is incorrect because $r \leq 180$ represents a maximum reduction, not minimum. Choice C is incorrect because while this is a valid intermediate step, it's not solved for $r$, and the question asks for minimum reduction, not the resulting emissions. Choice D is incorrect because it suggests reducing by at least 500 tons, which would result in 180 tons or less, overshooting the target.