Hello!
What you want to do first is find out how much 1 note card costs. We can do this by dividing the 4.80 by 15 (because 15 note cards cost 4.80)
4.80 / 15 = 0.32.
To see how much 8 note cards cost, we multiply the 0.32 (per note card) by 8.
0.32 x 8 = 2.56.
So answer D is correct!
Hope this helped you!