Choice Choice D is the correct answer.

1. Start with the equation: $5x + 10 = 30$
2. Subtract 10 from both sides: $5x = 30 - 10$
3. Simplify: $5x = 20$
4. Divide both sides by 5: $x = \frac{20}{5}$
5. Simplify: $x = 4$
6. Verify: $5(4) + 10 = 20 + 10 = 30$ ✓

Choice Choice A is incorrect because this results from adding 10 to 30: $40$, then $40/5 = 8$. Wrong inverse operation.

Choice Choice B is incorrect because this is the value of $5x$. You need to divide by 5.

Choice Choice C is incorrect because this results from multiplying 20 by 5: $100$.