Math Practice Problems and Answer Key

Any Books for Cramming Math, Biology, Geography, Politics, and History? Urgently Needed!

I'm in seventh grade (I'll be in eighth grade in the second half of this year), and my exams are coming up in a few days. They'll cover what we learned last semester, but I've been reading novels nonstop and haven't studied at all! My teacher expects a lot of me, so I want to read something that'll help me catch up. Thanks~