4 robots build a roller coaster in 14 days. How long would it take a team of 7 robots to build the same roller coaster?
Let's call a "robot-day" the amount of work one robot can do in one day.
For 4 robots to build a roller coaster in 14 days takes (4 robots)*(14 days) = 56 robot-days.
For a team of 7 robots to build this same 56-robot-day roller coaster takes 8 days.
[56/7, because (7 robots)*(8 days) = 56 robot-days]