I'm going to guess that for the OP, their reader is already past this level, but sharing anyway for the benefit of others, as I think it's a great book for roughly around that age:

https://www.amazon.com/Prof-McSquareds-Calculus-Primer-Inter...

I was about 8 when I saw my mom's copy of this:

https://www.amazon.com/Prof-McSquareds-Calculus-Primer-Inter...

It was years before I started to actually understand the math, but I could hardly wait to get to calculus in school because this book made it look like so much fun.