Secondary problem with the equation

A and B duo in the 300 meter circular track practice long-distance running, the speed is 6 meters a second B's speed is 7 meters a second, if A and B duo ran the same time and in the same direction after a few laps to run B for the first time to catch up with A?

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Solution: Let B be able to catch up after running a X seconds.

According to the available meaning of the questions:

7X-6X = 300

X = 300

B Therefore, ran (300X/300) = 300 ring

A: (abbreviated).