Corbett Maths 5-a-day help

I'm doing the higher math pracise questions on this thing that CorbettMath does, where he gives 5 math questions a day as a "warm-up" sort of thing, but I'm stuck on question two right now.

I can't insert a picture but I can give a link

https://corbettmaths.com/wp-content/uploads/2013/07/feb-higher-8-pdf.pdf

It's the cumulative frequency graph one.

Thank you if you can help

The corbett site has a video for every topic they include in worksheets etc
https://corbettmaths.com/2012/08/09/reading-cumulative-frequency-graphs/