Question 494390
Distance(d) equals Rate(r) times Time(t) or d=rt; r=d/t and t=d/r

Let t1= time to travel from A to B
And let t2= time to travel from B to A

Now we are told that t1 + t2=5 and we know that:
t1=d/81 and
t2=d/54 soooooo:
d/81 + d/54 = 5 multiply each term by 162
2d+3d=810
5d=810
d=162 mi
t1=162/81=2 hours---------------------trip by car
and t2=162/54=3 hours--------------------trip by bus

Trip by car + trip by bus=5 hrs
2+3=5
5=5

Hope this helps---ptaylor