It takes 32 minutes for 3 people to paint 4 walls. how many minutes does it take 4 people to paint 7 walls?

We order these data:

32 minutes3 people4 walls
x4 people7 walls
The minutes and the people are variables inversely proportional , therefore, we multiply in parallel
32 minutes*3 people=x*4 people

The minutes and the walls are variables directly proportinal; therefore, we  multiply cross.
32 minutes*7 walls=x*4 walls

Therefore:
32 minutes*3 people*7 walls=x*4 people*4 walls
x=(32 minutes*3 people*7 walls) / (4 people* 4 walls)
x=42 minutes.

the time will be 42 minutes.

Just divide the x axis (the top) by 2 or multiply the y axis (the bottom) by 2