Because in the breeze, a sailboat arrived from A to B for 3 hours.

Distance = the speed in the breeze times the time, so the distance between Party A and Party B is 3Km.

Quadratic time equation: one-third travel time +8km travel time+last travel time minus 0.6h = 3h.

Then it is (3v/3)/v+8/(2v/5)+[(2/3) * (3v)-8)/2v-0.6 = 3.

The solution is v v= 10/0km/h, so the distance is 3v = 3 *10 = 30km.