Answer:
16 minutes
Step-by-step explanation:
The number of minutes is expected to be proportional to the number of walls and inversely proportional to the number of minutes. Relative to the effort given, the number of walls is a factor of 4/9, and the number of people is a factor of 7/4. Hence the number of minutes will be ...
(63 min)×(4/9)×1/(7/4) = (63 min)×(16/63) = 16 min
It will take 16 minutes for 7 people to paint 4 walls.
