Choice Dhoice C is the correct answer.

1. Start with the equation: $9x - 18 = 27$
2. Add 18 to both sides: $9x = 27 + 18$
3. Simplify: $9x = 45$
4. Divide both sides by 9: $x = \frac{45}{9}$
5. Simplify: $x = 5$
6. Verify: $9(5) - 18 = 45 - 18 = 27$ ✓

Choice Dhoice B is incorrect because this results from subtracting 18 from 27: $9$, then $9/9 = 1$. We must add to undo subtraction.

Choice Dhoice D is incorrect because this is the value of $9x$. Don't stop early!

Choice Dhoice C is incorrect because this results from multiplying 45 by 9: $405$.