It sounds like your book is asking "what is the probability that the card is either a black card or a 9"
If so, there are 26 black cards (13 spades and 13 clubs) and four cards that have "9" on them (one in each suit). We have 26+4 = 30 cards that are either one or the other. There is overlap though. Namely the 2 black cards that have "9" on them (we count them twice), so we should subtract to get 30-2 = 28
There are 28 cards that either have a '9' on them, they are black, or both
This is out of 52 cards total
Divide the two values: 28/52 = 14/26 = 7/13 = 0.53846
Answer as a fraction: 7/13
Answer in decimal form: 0.53846
Answer as a percentage: 53.846%
Side note: the decimal form and percentage form are approximate