Mathematical probability problem in senior high school

If you extract one at a time and don't put it back, then the probability of each individual being extracted every time is the same, so it is one third.

For example, if you choose three out of ten people, the probability of each person being selected for the first time is one in ten, and there are only nine people left for the second time. The probability of each person being selected is 9/ 10 times 1/9, that is,110, because none of these individuals were selected in the first extraction, it is considered as the second time.