Question 294484
I was about to answer this out of turn, but then I saw the ending " please hurry to answer this."
You do realize we are volunteer tutors. We don't get paid.
Why should we put your problem ahead of the others who were here first?

I will give you a few hints.
What was the total of his first 4 tests?
Add that to his new average (x) and divide by 4+1
What will you set it equal to?

A second  way
What will the new total be if he gets an average of 80 on 5 tests?
 
A third way
Add up every time he missed 80 on the first four tests and add that to 80 for the grade he has to get on the fifth test.
 Hint: He isn't going to do it. Possible but not likely.