When a symbol is used for a number it could be any symbol at all. It could be a letter from the Roman or Greek alphabet, upper case or lower case. It could also be any random symbol that you like provided that it is not a "reserved" symbol. By that I mean you cannot use "+" as a symbol since that might be very confusing!
it is any letter or mathematical symbol that represent a number or a set of number
The greater than symbol is typically a mathematical symbol declaring that one given value or number is greater than another given value or number. One would use this symbol for certain mathematical applications, as well as to indicate in any circumstance that one things value is greater than another.
Q is the set of all rational numbers. The letter Q is used because rationals can be expressed as a quotient of two integers. Any letter from the Greek or Latin alphabet may be used as a symbol for an individual rational number.
variable
after
The cube symbol is the number 3 in a superscript format (Any number³)
it is any letter or mathematical symbol that represent a number or a set of number
1()
it is a variale
It can have any relation symbol - provided the relation is stated correctly.
9876543210
X
yes
The symbol for number is #
I will assume that you mean " to the power of two ". A symbol for any n-power is to put the number (n) on the side, above the number. Like this: nn.
The number of protons in any atom of any tungsten isotope is 74, the atomic number of tungsten. (W is the chemical symbol for tungsten.)
No. Radical(1.21) = 1.1, for example, is rational.