Answer:
Grade drops 9 percentage points.
New overall grade is 89%
Explanation:
The test with a score of 80% accounts for 50% of the grade.
The current average of 98% accounts for the other 50% of the grade.
50% of 80% + 50% of 98% =
= 40% + 49%
= 89%
The new overall grade is 89%.
Since the previous overall grade, before the test, was 98%,
and 98% - 89% = 9%, then
the new grade is 9 percentage points lower than the previous overall grade.