So if 2 people take 9 hours to paint the room and you want to know how long it will take if 3 people were painting first you will have to find the slope, or the rate of change, to do this you have to divide 9/2. 9/2= 4.5 So it take 4.5 hours for one person to paint the room. Therefore if there where three people painting it would be 3 x 4.5= 13 hours and 30 minutes. The time it would take to paint the room would increase.
