Your grades are calculated using a "weighted total". This means that every assignment and evaluation is worth a % of your final mark out of 100%.
How to calculate your weighted total is simple. You need your course outline and addendum. This tells you what each evaluation is worth. See the following example:
This is what you will see on your course outline or addendum:
Paper #1 is worth 30%
Test #1 is worth 20%
Test #2 is worth 20%
Paper #2 is worth 30%
Total course evaluation is worth 100% (30%+20%+20%+30%)
You will need to calculate your grade from the assignments mark. See example:
Paper #1 you got 45/55 marks
Paper #2 you got 50/65 marks
Test #1 you got 25/40 marks
Test #2 you got 30/65 marks
Now you need to convert them to their "weighted grade". See example:
Paper #1: 45/55 marks = 24.54% out of 30%
Paper #2: 50/65 marks = 23.07% out of 30%
Test #1: 25/40 marks = 12.5% out of 20%
Test #2: 30/65 marks = 9.23% out of 20%
Now add the % up:
69.34% out of 100%
Your final weighted total is 69.34% which translates to C+ grade.
If you need support with the math there are online weighted grade calculators.