Answer:
C
Step-by-step explanation:
I didn't use your formula bc I do not understand it =). I just did 975 divided by 780. When you do this you will get 125. This means that 975 is 125% of 780. So it has to be 25% more than 780. You can see that 780 divided by 4 (25 times 4 is 100 so 25 % is one fourth) is 195. Then 780 plus 195 is 975.
Hope this helped you!