The correct answer should be B.
However, since these only involve addition, the parentheses do not actually make a difference in the answer.
![a_n=a_{n-1}+7 \ \ \to \ \ d=7 \\ \\ a_n=a_1+d(n-1) \\ a_n=17+7(n-1) \\ a_n=17+7n-7 \\ a_n=7n+10](https://tex.z-dn.net/?f=a_n%3Da_%7Bn-1%7D%2B7%20%5C%20%5C%20%5Cto%20%20%5C%20%5C%20d%3D7%20%5C%5C%20%20%5C%5C%20a_n%3Da_1%2Bd%28n-1%29%20%5C%5C%20a_n%3D17%2B7%28n-1%29%20%5C%5C%20%20a_n%3D17%2B7n-7%20%5C%5C%20a_n%3D7n%2B10)
The answer is B. a_n = 7n+10
9. -4/15
10. -1/14
11. -3/4
12. -1/4
13. 11/17
14. -18/13
15. undefined
16. -30
from what I know
A=4
B=3
C=2
and a plus adds 0.33 and a minus minuses 0.33
question wants us to find yearly average or average per 1 year
since these grades span over 2 years, we must divide the total average by 2
averagefresh=sum of fresh grades/4 grades per year
averagesoph=sum of soph grades/4 grades per year
yearlyaverage=(averagefresh+averagesoph)/2
freshman:
(C)+(B)+(A)+(C-)=2+3+4+(2-0.33)=10.67
sophomore:
(B+)+(A-)+(C+)+(B-)=(3+0.33)+(4-0.33)+(2+0.33)+(3-0.33)=12
averagefresh=10.67/4=2.6675
averagesoph=12/4=3
yearlyaverage=(2.6675+3)/2=2.83375
so it's about a
average