The right answer is -13/12.
Remember, the volume formula of a sphere is

.
Set that equation equal to whatever volume they give you and solve for r.

=

Now solve for r! I know you can do this. If you need help, just comment.
It is a they need 27 canoes.
Answer:
c. 
Step-by-step explanation:
The x-1 is there because you can see that the starting point is 1 left from the y axis, and +4 because it starts four points above the x axis.