Traveling Men

Two men starting from the same point begin walking in different directions. Their rates of travel are in the ratio 7:3.  The slower man walks towards the east.  His faster companion walks to the south a distance of 10 pu and then turns towards an intercept course and proceeds until both men meet. How many pu did each man walk?

Jiuzhang Suanshu (The Nine Chapters on the Mathematical Art), c. 100 BCE

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