It takes 63 minutes for 4 people to paint 9 walls.How many minutes does it take 7 people to paint 4 walls?

63 / 9 = 7
7 / 4 = 1.75
It takes 1.75 minutes for 1 person to paint 1 wall...
1.75 * 4 = 7
7 * 7 = 49
It took 49 minutes for 7 people to paint 4 walls...