Watch: What is a number line? A number line can be used to add and subtract. Watch the video to learn what a number line is, and how to use it! A number line is a great way to add and subtract.

themselves and 1. 19 is a prime number. It can only be divided by 1 and 19. 9 is not a prime number. It can be divided by 3 as well as 1 and 9. Looking for even more resources to help engage ...