Not if you have purchased them and they belong to you.
The catch there is "illegal" which means "is it against some law" if that is what you meant to ask then the answer is good. If you are thinking in terms of a text book that belongs to someone else, like a school, yes you are responsible for the quality of the book you return to the school.
If you are in college and you intend to sell the book back after the class is over, it is "nice" not to us a highlighter or to write in them, but they will be bought back in spite of your notes.
In general, it is not illegal to write in textbooks that you personally own. However, if the textbooks belong to a school or institution, they may have rules against writing in them.
Write history novels / textbooks Write Re novels / textbooks Become a historian Research ... Work at Tescos
You can find a simile worksheet in textbooks or the textbooks website. In textbooks you can photo copy the page so you wouldn't have to write in the textbooks and on the textbooks website you can print out the worksheet.
Bob had 3 crates. He had 5 calculus textbooks in each. How many calculus textbooks in all? 15 calculus textbooks.
My classroom has 5 textbooks.
No.
no
yes
It was illegal.
Its illegal.
Sure, you can rent textbooks.
yes
It was illegal to what? Can you please provide more context so I can assist you better?