Write an algebraic expression for the sum of a number and three

I think it just meant to use (x) as a number, so just x+3, where x can represent any number 

Can you please add more information please? I don't know what numbers to use, so please include more information?

That is all the problem states with no numbers

So, can I use any number?

if yes, here it is!

$$52+3+a$$

I think that is an algebraic expression.

hope that this helps!

I guss so. And later on, you can learn more difficult expressions with algebra.