How can i get my grades points by now?

i live in puerto rico, we start high school in 10 grade, so when we go to university the years that count are 10 grade and up, so when i was in 10 grade, i got 2 point C in average, when i started 11 grade, someone changed the average thingy, and now we work different with the average, so what i want is to learn how to get my average, if i have 70%-C in math, 96%-A in science-chemistry, 65%-D in history and whatever, how can i get the total average in the school year, and after i get the total average, how can i get the average of 10, 11 and 12 grade together?How can i get my grades points by now?
In the, typical grading system is 60=D - lowest passing score, 70 = C, 80 =B, 90-100=A

A=4.0

B=3.0

C=2.0

D=1.0

If you took 2 classes and got a B and a C - say a 83 avg and a 75 avg, your GPA would be 2.5 (2.0 + 3.0)=5/2=2.50



Every school district may be different. You have to check with your school office and see how they plan to do it.



Bob