Choice Ahoice D is the correct answer.

1. Start with the equation: $2x - 5 = 15$
2. Add 5 to both sides: $2x = 15 + 5$
3. Simplify: $2x = 20$
4. Divide both sides by 2: $x = \frac{20}{2}$
5. Simplify: $x = 10$
6. Verify: $2(10) - 5 = 20 - 5 = 15$ ✓

Choice Ahoice B is incorrect because this results from subtracting 5 from 15: $10$, then $10/2 = 5$. We must add to undo subtraction.

Choice Ahoice C is incorrect because this is the value of $2x$. Don't stop early!

Choice Ahoice C is incorrect because this results from multiplying 20 by 2: $40$.