The current of a river is 5 miles per hour

Question

The current of a river is 5 miles per hour. A boat travels to a point 171 miles upstream and back again in 28 hours. What is the speed of the boat to the nearest tenth in water without a current? 

Answer 1

(b+5)x =171=(b-5)(28-x)

b=14 mph= boat speed

x=9 hours down stream

28-x=19 hours upstream