Equation to calculate what you would need to get a 98 average

Question

What equation would you use to calculate what grade you would need to get a grade of a 98 average?

 

Ex.

 

If you have a 1st semester average of 89. What 3rd and 4th quarter grades would you need to get an average of 98 with the first and second semester combined?

 

Thank you so much! Sorry I'm bad at explaining. 

Answer 1

Let x = the 2nd semester average

x + 89 = 98

    2

x + 89 = 196

x = 107

 

So, the sum of the 3rd and 4th quarter grades would have to equal 107.