Question 833021
Try it this way:
geoffrey drove g mph on the way to visit his parents. on the way back to school he drove r mph and it took him k hour less time then it did to drive to his parents house.


______________speed____________time______________distance
going_________g________________t_________________d
returning_____r________________t-k_______________d


Known variables: g, r, k
Unknown variables: t, d
Variables Assigned as g=60, r=75, k=1


Equations possible from data:
{{{gt=d}}}, and {{{r(t-k)=d}}};
The system is linear for t and for d.  The simplest thing to do is equate the two expressions for d, and first solve for t.