Probelm Solving linear equations with two variables (using either method)

Question

A canoe was paddled foe 2 hours with a 4km/h current.  The return trip against the current took 10 hours.  How fast can the canoe be paddled in still water?

Answer 1

distance=rate*time

d=rt

d=(r+4)2 (with the current)

d=(r-4)10 (against the current)

they are both equal to d so set them equal to each other

(r+4)2=(r-4)10

2r+8=10r-40

40+8=10r-2r

48=8r

48/8=r

r=6 km/hr in still water