Solution: Suppose the distance between the two cities is X kilometers, and the distance from the west city is 2 10Km, which is A,

Then, after driving forward for 20% of the whole journey, I drove 0.2X to Xicheng. Let this point be B? (that is, a? The distance to b is 0.2X)

Because the ratio of the distance traveled to the distance not traveled at this time is 3:2.

So the journey is 2/5 of the whole journey? That is, the distance not traveled is 2X/5Km,

That is, point B is 2X/5Km away from Xicheng.

Distance from A to Xicheng = distance from A to B+distance from B to Xicheng

So there's an equation? 0.2X+2X/5=2 10

Solve the equation? X=350？ (km)

Drawing a sketch helps to understand.

So the east and west cities are 350 kilometers apart.

The answer is as above, I hope it will help you.