Shelby,
To calculate how many 5 card hands contain at least one black card it is easier to calculate how manny hands have no black cards and the subtract this from the total number of 5 card hands.
number of 5 card hands containing no black cards= 26C5=67,780
Total number of five card hands=52C5=2,598,960
Number of hands containing at least one black card=2,598,960-67,780=2,531,180.
We are using the principle that N(5 card hands)=N(5 card hands / no black cards)+N(5 card hands/at least one black card)
Hope this helps
Jim