Choice A is the correct answer. Rewrite in slope-intercept form.

1. Isolate y: Subtract $3x$ from both sides.
2. Equation: $y = -3x$.
3. Slope: The coefficient of $x$ is $-3$.

💡 Strategic Tip: For $Ax + By = C$, the slope is always $-A/B$. Here $-3/1 = -3$.

Choice B is incorrect because it misses the sign change. Choice C is incorrect because it flips the fraction. Choice D is incorrect because it confuses the intercept (0) with the slope.