University of Waterloo, University of Windsor, and University of Toronto. I just need to know the minum average in high school i need to get in there

Different major will have different requirement. Please specific the major on each University

I'm not too sure about the minimum average, but I know someone that got into U of Windsor with 68.
You can probably find a lot of those information from booklets in your school's guidance office.  Or you can go to each of the school's website and look under "admission".
If you have an average about 85, you can get into most schools.

go to each university's website and find admission requiement--> then u will c the min average