I am an ICSE student and I have some problem in mathematics regarding linear inequations.
In some examples I have found x $\in$ R and I have also found x $\in$ Q .
I know that 'R' means rational numbers, but can anybody explain me what is 'Q' and which numbers are allowed ? Are both of them similar or is there some difference between the two ?
Also, please tell me the difference between I and Z.