Answer:
6 ft/min
Step-by-step explanation:
Theres a neat trick to note; whenever you say per think of it as a fancy word for divide, because the label is always gonna be a/b (a per b)
Therefore,
the rate of feet per minute will be the feet divided by the minutes;
18 feet in 3 minutes = 18/3 ft/min
Therefore the rate is 6 feet per minute.
IF you need an explanation on what average rate implies:
Note; the word average is not prudent to answer as its extraneous, however if there was more data like "Cami descends 18 ft in 3 min and Nami descends 9 ft in 3 minutes; whats the average rate at which they descend" then you'd have to add the two rates up and divide by two.
Hope this helps :)
