Question

on a canoe trip, Rita paddled upstream (against the current) at an average speed of 2 mi/hr relative to the riverbank. on the return trip downstream (with the current), her average speed was 3 mi/hr. find rita's paddling speed in still water and the speed of the river's current.

dealing w/- substitution and elimination

Answer 1

let w be the water speed
let b be the boat speed in still water.

b-w=2
b+w=3

solve. I would add the two equations to eliminate w.

Answer 2

b-w=2

b+w=3 (transpose)
b=3-w (substitute)
3-w-w=2 (combine like terms)
-2w=-1 (cancel -2)
w= 1/2