Choice Ahoice D is the correct answer. We solve this two-step equation by isolating the variable term first.

1. Start with the equation: $3x + 4 = 19$
2. Subtract 4 from both sides: $3x = 19 - 4$
3. Simplify: $3x = 15$
4. Divide both sides by 3: $x = \frac{15}{3}$
5. Simplify: $x = 5$
6. Verify: $3(5) + 4 = 15 + 4 = 19$ ✓

Choice Ahoice C is incorrect because this results from adding 4 to 19: $23$, then $23/3 \approx 7.66$. We must subtract to undo addition.

Choice Ahoice C is incorrect because this is the value of $3x$. You must divide by 3 to find $x$.

Choice Ahoice D is incorrect because this results from multiplying 15 by 3: $15 \times 3 = 45$. Division is the correct inverse operation.