The first hour is 5 kilometers less than the second, so the second hour in Pinglu Mountain is:

5÷6=5/6 hours =50 minutes

So Li Gang climbed the slope in 60×2-50=70 minutes.

Let Li Gang ride uphill 10 minutes x kilometers, then Li Gang rides uphill 6x kilometers per hour, flat road 6x+6km per hour and downhill road 6x+9km per hour.

The uphill road is 7x kilometers.

Li Gang walked 6 kilometers in the first hour-all on the way up the mountain.

In the second hour, I ran 6x+5km-including X km uphill and 5x+5km flat road.

The third hour is 6x+8km-including all downhill roads and a flat road.

The downhill distance is the uphill distance: 7x kilometers.

Then the flat road distance of the third hour line is: 6x+8-7x = 8-x.

kilometre (km)

Then the distance of the flat road is: (5x+5+8-x)÷2=2x+6.5.

kilometre (km)

The third hour includes 8-x kilometers of leveling time and 7 kilometers of downhill time:

(8-x)/(6x+6)+7x/(6x+9)= 1

(8-x)(6x+9)+7x(6x+6)=(6x+6)(6x+9)

-6x？ +39x+72+42x？ +42x=36x？ +90x+54

9x= 18

x=2

The distance of uphill (downhill) road is 7× 2 = 14km.

The road leveling distance is 2× 2+6.5 =10.5km..

The downhill speed of Li Gang is 6×2+9=2 1 (km/h).

Used: 14÷2 1=2/3 hours =40 minutes.

Distance between Party A and Party B:14+10.5 = 24.5km.

A: It took Li Gang 70 minutes to go uphill and 40 minutes to go downhill. The distance between a and b is 24.5 kilometers.