Please explain how you got the answer so I can understand how to do them in the right way !

9/10 divide by -3/15 as a mixed number

Starting at home, emily traveled uphill to the hardware store for 606060 minutes at just 666 mph. she then traveled back home along the same path downhill at a speed of 121212 mph. what is her average speed for the entire trip from home to the hardware store and back?

What is the inverse of the function below? f(x)=x/3-2