Choice Bhoice D is the correct answer. Even with negative results, the solution strategy remains the same.

1. Start with the equation: $x - 30 = -10$
2. Add 30 to both sides: $x = -10 + 30$
3. Calculate: $x = 20$
4. Verify: $20 - 30 = -10$ ✓

This shows that we can get a positive solution even when the right side is negative.

💡 Working with Negatives: When adding a positive to a negative, think: $-10 + 30 = 30 - 10 = 20$.

Choice Bhoice C is incorrect because this results from adding 30 to the absolute value: $10 + 30 = 40$ (ignoring the negative sign).

Choice Bhoice D is incorrect because this might come from subtracting instead of adding: $-10 - 30 = -40$. This applies subtraction twice.

Choice Bhoice C is incorrect because this is the negative of the correct answer. Some students might calculate correctly but then mistakenly apply a negative sign.