Choice Choice B is the correct answer. To eliminate the fraction, we multiply both sides by the denominator.

1. Start with the equation: $\frac{x}{15} = 3$
2. Multiply both sides by 15: $x = 3 \times 15$
3. Calculate: $x = 45$
4. Verify: $\frac{45}{15} = 3$ ✓

💡 Check Your Work: You can verify mentally: "45 divided by 15 is 3" or "15 times 3 is 45."

Choice A is incorrect because this results from adding: $15 + 3 = 18$. Addition is not the inverse of division.

Choice B is incorrect because this comes from dividing 15 by 3 instead of multiplying: $\frac{15}{3} = 5$. This is backwards.

Choice D is incorrect because this results from dividing 3 by 15: $\frac{3}{15} = 0.2$. This divides in the opposite direction.