Abicyclist bikes the 90 mi to a city averaging a certain speed. the return trip is made at a speed that is 1 mph slower. total time for the round trip is 19 hr. find the bicyclist's average speed on each part of the trip.

his speeds while going to city is 10 mph and while his round trip the speed will be 9 mph

Explanation:

Let say the speed of the bicycle while he moves towards the city is "v"

now the speed of the round trip must be smaller by 1 mph

so its speed for round trip will be

now we know that total time of the motion is 19 hr

so we will have

so we will have

by solving above equation we have

so his speeds while going to city is 10 mph and while his round trip the speed will be 9 mph

i don't understand. explain it clearly