Mathematics - Pre-Algebra - Variables and expressions - The Mystery Box

Show a mystery box with a '?' inside. '? + 5 = 8. What's in the box?' Options: 2, 3, 4, 5. Do 5 rounds with simple equations. Then reveal: in algebra, instead of '?', we use letters like x. 'x + 5 = 8' means the same thing! The student sees that variables are just placeholders for unknown numbers.