- The Mongols used qualified people wherever they were needed/Mongols placed Arabs in Russia/Persians in China because they were qualified
- Working bureaucracies were kept in place
- Many local rulers maintained their position as long as they paid tribute/provided troops/pledged loyalty/kept good order
- Chinese bureaucrats still did their jobs as long as they did not cause the Mongols any trouble
- Local Persian rulers stayed in power if they cooperated
These are five examples of answers, hope one can help you!