Choice Dhoice D is the correct answer.

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

Choice Dhoice B is incorrect because this results from adding 8 to 20: $28$, then $28/2 = 14$. Wrong inverse operation.

Choice Dhoice C is incorrect because this is the value of $2x$. You need to divide by 2.

Choice Dhoice A is incorrect because this results from multiplying 12 by 2: $24$.