Answer:
When you selected the math book, it was an independent event.
However, when you selected the notebook, it was a dependent event.
The math book is an independent event because it's selection doesn't depend on anything else...it's the first thing you chose. However the notebook is a dependent event because you did not put the math book in the bag after you took it out. Therefore, because you selected the math book first, you only had 9 items to choose from as opposed to 10 if you had put the math book back.