It takes 60 minutes for 7 people to paint 5 walls. how many minutes does it take 10 people to paint 10 walls?

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. 

X= 49; x = 4step 1: foilstep 2: equal both to 0step 3: find x individually

The answer should be 5.