Very simple equation application problem ah, well written to 100! A and B walk from two places 20km apart at the same time. The speed of a and B is 6km and 4km respectively. A dog and a start to run to B at the same time. When they meet B, they run to a immediately. When they meet a, they turn around and run to B immediately until they meet. If the dog runs at 13km / h, what is the running speed, How many kilometers does the dog travel?

Very simple equation application problem ah, well written to 100! A and B walk from two places 20km apart at the same time. The speed of a and B is 6km and 4km respectively. A dog and a start to run to B at the same time. When they meet B, they run to a immediately. When they meet a, they turn around and run to B immediately until they meet. If the dog runs at 13km / h, what is the running speed, How many kilometers does the dog travel?

The dog's speed is multiplied by the time it takes for two people to meet
13*（20/（6+4））=26