It takes 54 minutes for 4 people to paint 6 walls. How many minutes does it take 6 people to paint 7 walls?
54 min * 4 people / 6 walls = 36 min-people/ wall
36 min-people/wall x 7 wall/6 people = 42 min
If 6 walls can be painted in 54 min.....then 1 wall can be painted in 9 min
Which means that each person can paint 1 /( 9 * 4) = 1/36 of the wall in one minute
So 6 people can paint 6 (1/36) = 1/6 of a wall in 1 minute
So....the number of minutes that it would take them to paint 7 walls =
7 / (1/6) = 7 * 6 = 42 min