There have been 5 tests so far.
The final will count for two more.
So the grand average score will be the average of 7 test scores.
If the grand average score is to be 80, then all 7 components
will add up to (7 x 80) = 560 .
The tests she has already taken add up to
(75 + 84 + 74 + 59 + 94) = 386
So the "two" tests she's about to take need to add at least
(560 - 386) = 174 .
So she needs to score at least (174/2) = 87 on the final.
It'll be averaged into the others as if it were two tests,
so it'll add 174 points to the others, and the whole set
of ' 7 ' tests will average 80 .
