What happens when you want to show with math that there is nothing? That is where we use zero (0). So 3 - 3 = 0. When you have no money, you have $0 (zero dollars).

So far we have learned about nine different numbers. But what if we want to count higher than nine? This is where we use numbers that have more than one *digit*.

9 + 1 = 10

- At first, this looks like nonsense. How can nine and one make "one-zero"? But the "one-zero" is actually a number in itself. Since there is more than one digit, all but the last digit represent numbers larger than nine. 10 can be rewritten as 1 × 10 + 0.

- 15 = 1 × 10 + 5
- 30 = 3 × 10 + 0
- 58 = 5 × 10 + 8