Dividing by 10 is pretty easy. Take a look at a few really easy examples:
80 / 10 = 8
90 / 10 = 9
20 / 10 = 2
50 / 10 = 5
Now take a look at these examples.
900 / 10 = 90
9000 / 10 = 900
80 / 10 = 8
800 / 10 = 80
Try a few for yourself!