It takes 7 hours for 12 men to paint a room.

How many men would be needed to paint the room in 3 hours?

28 men would be required to paint the room

Step-by-step explanation:

if every man work independently of the others in the room (that means that each one works in parallel without interrupting the others).

time required to paint = time that each men worked * number of man that worked in the room = 7 hours / men * 12 men = 84 hours

since the time required to paint the room is 84 hours, if we have need to finish in 3 hours, the number of men that should be working are

time required to paint = time that each men worked * number of man that worked in the room

or

number of man that worked in the room = time required to paint / time that each men worked = 84 hours / 3 hours/men = 28 men