How much text material can you use in a report you create for another class?
You can use limited material of another's copyrighted work without asking permission from the owner. This is called the "Fair Use" rule. Under the "Fair Use" rule of copyright law, an author may make limited use of another author's work without asking permission. Go to http://www.nolo.com/legal-encyclopedia/fair-use-rule-copyright-material-30100.html for details.
If it's your work, you can use it all.
You should learn to use "footnotes" so if you quote another person's work, you can give credit.