Answer:
5 minutes
Step-by-step explanation:
it dives at positive 18 feet in a minute
however in order to dive at -54 feet, it must dive -5 times
18-18-18-18-18= -54
and 1min =18feet
so it needs 5minutes for the 5times
OR
Let x=the time needed to dive at -54 feet's
so 1min=18
x= -54
-54=18x
dividing both sides by 18
-54/18=18x/18
x=-54/18
x=-5
however time cannot be negative
therefore x =5
this implies that the penguin dives at -54 feet in 5 minutes.
