Informal: 你叫什么名字?(nǐ jiào shén me míng zi) What are you called?
Informal: 我叫。。。(wǒ jiào…) I’m called…
This is the most common and polite way to ask someone’s family name in Chinese, however, in general it is not customary to simply ask for the family name:
Polite: 你贵姓?(nǐ guì xìng) What is your family name?
To subject is basically counting down from the biggest number from the lowest so say u have 5-2 because two is the lowest u have to subtract 5 from two to get your answer 4 3 get it?