What is the speed of the current?

Question

It takes 3 hours for a boat to travel 27 miles upstream. The same boat can travel 30 miles downstream in 2 hours. What is the speed of the current?

Answer 1

27 = (R-S)*3

30 = (R+S)*2

distributive

27 = 3r - 3s

30 = 2r + 2s

solves by elimination

54 = 6r - 6s

90 = 6r + 6s

144 = 12r

r = 12

30 = (12 + s)*2

30 = 24 + 2s

6 = 2s

s = 3

The speed of the boat is 12 and the speed of the current is 3