We would need to know if the grades are
being calculated by averaging the point values
of the letters or averaging the percents.
If you are in public high school, they are probably
averaging the letters. I also need to know whether
they use A+, A- B+ B B- or simply use
A B C D F and your school systems faculty rules
for determining the cutoff for an A. Some schools will
use , on A B C D F with no plus/minus a cutoff as low
as 3.5 . Some use 3.60 or 3.75 . If the cut is 3.5 and
you have an A for third semester and an A for 4th semester
then you need your exam grade to satisfy
3.5 = 0.45*4+0.45*4 + 0.10x
so
3.5 - 0.9*4 = 0.10x
so
That means you only need -0.10/0.10 = -1
which is one full grade below an F
However, suppose you need 3.75 and you have 2 A's
Now you need
3.75 - 0.9*4
▬▬▬▬▬▬ = 1.5
....0.1
That is halfway between a D and a C. A D would not
do it. If there are no plus/minus grades and 3.75 is
needed to get an A in the class, then you need a C
on the Final Exam.
If you have an A and a B for term grades, then you need an A on your final to get
an A.
If you have an A and a C or no A's at all, you are not getting an A, unless
you have a teacher who can override the usual rules for calculating grades and
that does not happen in high school. In college, some of us like to give an A in
the course to any student who can earn an A on the final. However, in classes
where we allow that, the average student gets two letter grades less on their
final exam than they have earned all quarter or semester.