Analysis: Let the local train speed be Xkm/h, and the express train speed be (x+20) km/h..

The local train drove 50% of the whole game in 2 hours, which means 2*X= half of the whole journey. That is, the whole journey is 4xkm.

After the express train has been driving for 2 hours, there are still 300 kilometers left, so the whole journey is 2*(X+20)+300 kilometers.

As can be seen from the above, 2*(X+20)+300=4X.

Calculated x =170 km/h.

Then the whole journey =4*X=4* 170=680 km.