Choice A is the correct answer. Set $y=0$.

1. Substitute: $0 = 3x - 12$.
2. Add 12: $12 = 3x$.
3. Divide: $x = 4$.

💡 Strategic Tip: In $y=mx+b$, x-intercept is $-b/m$.

Choice B is incorrect because y-intercept. Choice C is incorrect because sign error. Choice D is incorrect because calculation error.