Choice Choice D is the correct answer.

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

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

Choice Choice C is incorrect because this is the value of $4x$. Don't stop early!

Choice Choice B is incorrect because this results from multiplying 20 by 4: $80$.