If 12 People Are Needed To Run 4 Machines, How Many Are Needed To Run 20?

This question can be written as:
12 people = 4 machines
X people = 20 machines
Cross multiplying:
4*x=20*12
So:
4x=240
dividing:
x=240/4
Hence:
x=60
So 60 people are needed to run 20 machines