Respuesta :

The time (minutes) vary directly with the number of walls and inversely to the number of people.
m = kw/p, where m = minutes, w = walls, and p = people
60 = 5k/7
420 = 5k
84 = k m = 10(84)/10
m = 84

It takes 84 minutes for 10 people to paint 10 walls.