I would like to ask a question as below:
In a box, there are 2 white balls and 8 red balls. I draw a ball from the box and put it back. I do it for 6 times.
What is the probability that I draw a white ball after the experiment ?
Thank you for your help!
In this answer "..I draw a white ball after the experiment.." is interpreted as "..I have drawn at least one white ball after the experiment..".
Because the cards drawn are placed back you are dealing with $6$ independent events that can succeed or fail, and all have equal chance to succeed.
If $X$ denotes the number of white balls drawn then $X$ has binomial distribution with parameters $n=6$ and $p=\frac2{10}=0.2$.
The event that (at least) one white ball is drawn is $\{X\geq1\}$.
Can you take it from here?
Btw, also note that $\{X\geq1\}=\{X=0\}^{\complement}$ while $P(\{X=0\}^{\complement})=1-P(\{X=0\})$.