A boat sails 'm' miles upstream at the rate of 'r' miles per hour. The rate

Question

of the stream is 's' miles per hour. How long will it take the boat to return to its starting point?

Answer 1

upstream time is
m/(r-s)

downstream time is
m/(r+s)

Answer 2

I didn't understand why m/r+2s instead I got m/ r-s