Question

Laura and Brent paddled a canoe 6 miles upstream in four hours. The return trip took three hours. Find the rate at which Laura and Brent paddled the canoe is still water.

Answer 1

Call the rate in still water vs;
upstream you have: vs-v=6/4
downstram you have: vs+v=6/3
where v is the rate with which the river flows.
rearranging:
vs-v=3/2
vs+v=2
from the second you have v=2-vs substitute into the first:
vs-2+vs=3/2
2vs=7/2
vs=7 mi/hr