Final answer:
The average grade of the students who passed is 8.
Step-by-step explanation:
To find the average grade of the students who passed, we need to calculate the sum of their grades and divide it by the number of students who passed.
There are 20 students in total and 8 students failed with a grade of 3. This means that 20 - 8 = 12 students passed.
Let's calculate the sum of their grades: (12 * 6) + (8 * 3) = 72 + 24 = 96.
Now, divide the sum by the number of students who passed: 96 / 12 = 8.
Therefore, the average grade of the students who passed is 8.