Question

help.

Answer 1

Order your data from smallest to largest. Then, just count how many times you see values between 0-9, 10-19, etc.

the "how many times" you see that value is called the frequency

Answer 2

For example
You don't see any values between 0-9, so the frequency is 0
You see 1 value between 10-19 (which is the value "15" in the list), so the frequency is 1