Every course is weighting when they are initially built. Weighting is based on the lesson components of each course.
In the grade book you can view the weighting by clicking the dropdown here:
How weighting is calculated
Using this example:
Lessons are 30%
Exams are 35%
To calculate the weighted grade, you take the percentage from each category, multiply that by their respective weight %, add them together, then divide by the sum of the weights for those categories.
For this student, they have a total of 70 points from lessons out of a possible 80, which calculates to 87.5% -- multiply by the weight (30%) you get 26.25%
For quizzes, they have 40 out of a possible 50, for 80%, multiply by the weight (25%) and you get 20%
Added together this is 46.25%
Then you divided by the sum of the weights for those categories (46.25 / (30% + 25%)) = 84.09 %