Maths help please?

I had no choice but to leave school at a very early age due to bullying now as an adult I’ve decided to get an education but for the life of me I am stuck on this question

Organise the data into a frequency distribution with class intervals 10-19, 20-29

what are class intervals and what is the best way for me to work out the answer to this question TIA I really appreciate all the help thank you
Maths help please?
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