As for GPA you take ALL your grades and average them.

For example:

English 1 A = 4

Physical Science B = 3

World History C = 2

Bible A = 4

You would add 4+3+2+4=13 Then you divide your answer by the number of courses (in my example above there are 4 courses, so we divide 13 by 4. That would give you a GPA of 3.25

If you were doing multiple years you would still follow the same formula, The sum of all the grade points divided by the number of courses.

Only remember that only academic classes are usually counted in GPA, so things like P.E. are not counted, but health because it has an academic study element would be.

3.75 is pretty good.