Choice Choice D is the correct answer.

1. Start with the equation: $6x - 18 = 12$
2. Add 18 to both sides: $6x = 12 + 18$
3. Simplify: $6x = 30$
4. Divide both sides by 6: $x = \frac{30}{6}$
5. Simplify: $x = 5$
6. Verify: $6(5) - 18 = 30 - 18 = 12$ ✓

Choice Choice C is incorrect because this results from subtracting 18 from 12: $-6$, then $-6/6 = -1$. We must add to undo subtraction.

Choice Choice B is incorrect because this is the value of $6x$. Don't stop early!

Choice Choice C is incorrect because this results from multiplying 30 by 6: $180$.