Video narration
How many stickers did you start with if you add three more and end up with eight? That little sticker mystery is where algebra can help. You know the extra stickers and the total, but the starting pile is hidden. We can use a letter for that missing amount. In this puzzle, let x stand for your starting stickers. That letter is called a variable: a letter standing for a number we don't know yet. So the equation is x plus three equals eight. An equation is a number sentence saying both sides are equal. To uncover x, undo the adding. Subtract three from both sides, so the balance stays equal: x equals five. The letter isn't an extra mystery; it marks the number you're looking for. You started with five stickers: x was the missing number, revealed by subtracting three.