1. **State the problem:** It takes 48 minutes for 7 people to paint 7 walls. We want to find how many minutes it takes 20 people to paint 20 walls. 2. **Understand the relationship:** The problem implies that the work rate is proportional to the number of people and the number of walls. If 7 people paint 7 walls in 48 minutes, then the time taken per wall per person is constant. 3. **Calculate the rate:** The total work is 7 walls painted by 7 people in 48 minutes. So, the work done per person per minute is $$\frac{7 \text{ walls}}{7 \text{ people} \times 48 \text{ minutes}} = \frac{1}{48} \text{ walls per person per minute}.$$ 4. **Calculate time for 20 people to paint 20 walls:** The total work is 20 walls. The combined rate of 20 people is $$20 \times \frac{1}{48} = \frac{20}{48} = \frac{5}{12} \text{ walls per minute}.$$ 5. **Find the time:** Time is work divided by rate, so $$\text{Time} = \frac{20 \text{ walls}}{\frac{5}{12} \text{ walls per minute}} = 20 \times \frac{12}{5} = 48 \text{ minutes}.$$ **Final answer:** It takes 20 people 48 minutes to paint 20 walls.