Laura and Brent paddled a canoe 6 miles upstream in four hours. The return trip took 3 hours. What is the rate at which they paddled the canoe?

P = paddling speed

C = speed of the current

Upstream: 6 = 4 (P - C. Downstream: 6 = 3 (P + C)

4P - 4C = 6

3P + 3C = 6

12P - 12C = 18

12P + 12C = 24

Add the equations:

24P = 42. P = 42/24 = 1.75 mph

Subtract the equations:

-24C = - 6

C = 0.25 mph