If you earn an A in ENGL 463 and C in BIOL 198, ENGL 463 gets 4 points and BIOL 198 gets 2 points.
Now multiply that number times the number of credit hours assigned to the course. Do this for all your courses.
ENGL 463: 4 X 3 hours = 12 grade points BIOL 198: 2 X 4 hours = 8 grade points
Add your totals together.
12 (ENGL 463) + 8 (BIOL 198) = 20 grade points
Now divide that number by your semester credit hours. The result is your GPA for those courses.
ENGL 463 is 3 hours and BIOL 198 is 4 hours so 20 grade points divided by 7 credit hours equals a 2.85 GPA for the semester if those are your two classes.