The sum of 5 and a number

It seems we are looking for a math expression that is the same as English expression you wrote.The sum is what we get when we add numbers. Therefore, we could restate the English expression as what do we get when we add 5 to the number x? While we do not know what specific number x represents, we do know that if we add 5 to the number x we get 5 plus x. Now the question can be restated as, "How do we write 5 plus the number x?" Do you know the answer now? Does 5 + x sound right? How about x + 5? Both of these expressions are correct as they both represent the sum of 5 and the number x.