You can assign weights to categories to make certain types of assignments worth more than others. By default, all categories are weighted the same.
First, navigate to the Gradebook tab in the left-hand column. Choose Grade Setup.
Check the Weight Categories box to turn on weighted grading.
Click on the number in the Weight column to change it.
If you recategorize activities when assigning them, you may wish to assign a value of 0 to all categories other than Classwork, Homework, Quizzes, and Tests.
More information available here.