If the rent for the first year is X yuan, then the rent for the second year is (x+500) yuan.

96000/x= 102000/(x+500) (according to the same number of houses)

102000x=96000x+48000000

6000x=48000000

x=8000

Let the distance between each car be s.

S/(v people +v cars) =6 S=6(v cars +v people)

S/(v car -v people) =30 S=30(v car -v people)

6(v car +v people) =30(v car -v people)

V car +v people =5v car -5v people

V people =2/3 V cars

S/(v people +v cars) =6

S/(2/3v car +v car) =6

S/v car = 10

So every 10 minutes.