Question 886437
r is the speed on the first part of the trip.


________________speed_______time_______distance
First Part_______r__________(___)_________40
Second Part_____r-3_________(___)________100
TOTAL________________________2


RT=D basic law about uniform rates of travel.
T=D/R.


________________speed_______time__________distance
First Part_________r__________{{{40/r}}}____________40
Second Part_______r-3_________{{{100/(r-3)}}}________100
TOTAL________________________2


Solve for r in {{{highlight_green(40/r+100/(r-3)=2)}}}.


Solving that should pass some steps simplifying to {{{r^2-73r+60=0}}}, and general solution should be {{{highlight(r=72)}}} mph.  The other part of the trip is {{{highlight(r-3=69)}}} mph.