How do you write sum of a number?

To write the sum of a number, you typically express it as an equation or an algebraic expression. For example, if you want to represent the sum of the number ( x ) and another number ( y ), you would write it as ( x + y ). If you're summing multiple numbers, you can extend this to ( x + y + z + ... ). In formal mathematics, the summation symbol ( \Sigma ) can also be used to denote the sum of a series of numbers.