Question 818988
Speed of truck is r.


__________________speed_____________time____________distance
Bus_______________r-15______________(___)___________190
Truck_____________r_________________(___)___________135


We need time expressions for the equal time of both bus and truck:


__________________speed_____________time____________distance
Bus_______________r-15______________190/(r-15)___________190
Truck_____________r_________________135/r___________135


You should already sense a mistake in the given information.  Equal time, the bus is slower but traveled more miles than the truck.  This cannot be.  You mixed-up some information.


{{{190/(r-15)=135/r}}}
LCD r(r-15)
or
{{{135(r-15)=190r}}}
{{{135r-135*15=190r}}}
{{{135r-190r=135*15}}}
{{{-55r=135*3*5}}}
{{{r=-(135*3*5)/(11*5)=-135*3/11}}}


Why should we allow {{{r<0}}}?