The joint probability P(B′∪F) is given by the sum of each individual probability minus the intersection between both probabilities (red face cards).
The inverse probability of a card being black is also the probability of a card being red, which is 26 in 52. There are 12 face cards in a 52-card deck, 6 of which are not black, therefore:
subtract 70.4% from 90% to get 19.6% make the .2x into 2 and the 19.6 into 196 divide 196 by 2 to come up with the answer of 98%. you will need a 98% to have a 90% for the final grade