Algebra Variable

Hey Bloggers,
Today Room 4 maths class learned about Algebra Variable. What is Algebra Variable? Well what I have heard is that Algebra Variable means something that changes, e.g  5 + g = 9 so the g means 4 because
 5 + 4 = 9 so you just basically use a symbol or a letter so its really a mystery number. So here is what i have learnt and here is a presentation and please leave a comment.