1. **State the problem:** A painter uses 1.2 liters of paint to cover 1 square meter of wall. We need to find how many square meters he can cover with 12 liters of paint. 2. **Formula and explanation:** The amount of paint used is proportional to the area covered. If $1.2$ liters cover $1$ m$^2$, then the area $A$ covered by $12$ liters is given by: $$A = \frac{\text{Total paint}}{\text{Paint per m}^2}$$ 3. **Calculate the area:** $$A = \frac{12}{1.2}$$ 4. **Simplify the fraction:** $$A = \frac{\cancel{12}}{\cancel{1.2}} = 10$$ 5. **Interpretation:** The painter can cover $10$ square meters with $12$ liters of paint. **Final answer:** He can cover 10 m$^2$ with 12 liters of paint.