Answer:
8c2 = 28
Explanation:
You can plug this into your calculator (on a TI-84, it's MATH -> PRB -> 3) as 8 nCr 2.
Let's try to understand what the output means, though! The nCr function is based on Pascal's Triangle (see the attachment for a picture).
When we do 8 choose 2, we are basically thinking about having 8 possible values and 2 spots to fit them in, and we don't care about what order they're in. The probability of this is 8*7 / 2 = 28. Our answer makes sense!