I would think it would be just -39 points
Answer:

Step-by-step explanation:
GIVEN: In the
school year in country A, there were
foreign students from country B. This number is
more than the number of students from country C.
TO FIND: How many foreign students were from country C.
SOLUTION:
Total foreign students from country B 
let the foreign students from country C be 
As the students from country B is
more than the country C
Students from country B



Hence the number of students from country C are 
Step-by-step explanation:
5x + 80 = 180
x = 20
2x = 40
3x=60
7x=140
115 divided 23/4 is equivalent to 115 x 4/23= 20
An = a1 + (n-1)*d
n = term to find = 30
a1 = first term = 20
d = common difference = 2
a30 = 20 + (30 - 1) * 2
a30 = 20 + 29 * 2
a30 = 20 + 58
a30 = 78
sn = (n (a1 + a30)) / 2
s30 = (30(20 + 78) / 2
s30 = (30(98) / 2
s30 = 2940/2
s30 = 1470 <===