Choice Choice D is the correct answer. We add to undo subtraction, then divide.

1. Start with the equation: $4x - 8 = 12$
2. Add 8 to both sides: $4x = 12 + 8$
3. Simplify: $4x = 20$
4. Divide both sides by 4: $x = \frac{20}{4}$
5. Simplify: $x = 5$
6. Verify: $4(5) - 8 = 20 - 8 = 12$ ✓

Choice Choice A is incorrect because this results from subtracting 8 from 12: $12 - 8 = 4$, then $4/4 = 1$. We must add to undo subtraction.

Choice Choice C is incorrect because this is the value of $4x$. The variable is not yet isolated.

Choice Choice B is incorrect because this results from multiplying 20 by 4: $20 \times 4 = 80$. We need to divide.