Answer:
28 men would be required to paint the room
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