Question 750254
Basic concept is rate*time=distance.  rate is miles per hour, time is hours, distance is miles.


You know the total time but you do not know each individual time for the two distances.  Know to do this:


{{{r*t=d}}}
{{{r*t/r=d/r}}}
{{{t=d/r}}}---------which you can use.


First Part, rate is r.
Second part, rate is r-5.


{{{highlight(200/r+225/(r-5)=10)}}}
The sum of the two parts of the times for the trip is 10 hours.  See, the equation has some rational parts, meaning take the form of fractions.