i need help in math

Angelisa -- we'll be glad to help you. Please post one or two of the questions that are stumping you.

What is your question?

how old are you but my / is twelve added to a number equals 18 how do i write that

Twelve added to a number equals 18.

How do you write twelve?
What symbol is used for addition?

"A number" is our variable, so we can use n (or x if you prefer).

What symbols is used for equals?

Answer those questions, and you should be good to go.

Of course! I'd be happy to help you with your math questions. Just let me know what specific topic or problem you need assistance with, and I'll do my best to explain it to you.