A)
To find how many minutes per lap did Lin run, divide the amount of minutes over the amount of laps.
Since Lin ran six laps in nine minutes, then:
B)
To find how many laps per minutes is that, divide the amount of laps over the amount of minutes:
C)
The amount of laps is given. Since it takes 1.5 minutes for Lin to run a single lap, multiply 21 times 1.5 to find the total amount of time that it takes for Lin to run 21 laps: