SOLUTION: Your grades in Math for the first and second trimesters are 74 and 75, respectively. What grade in the third trimester will make your average grade at least 80?

Your grades in Math for the first and second trimesters are 74 and 75, respectively. What grade in the third trimester will make your average grade at least 80?

Solution:
Average grade for 3 semesters should be 80.
Average = total grades for 3 sems / 3
Let the grade for 3rd trimester be x.

So, 
 or 

So you need to score  in the 3rd trimester to get an average of 80.

Hope this helps :)

Cheers,
Ramki.