Try this explanation:
according to the condition, 'set it aside'. It means, that the sum of f_magazines and h_magazines is 2+4=6.
Using this it is possible to re-write the finding the probability of the both events A&B:
P(A)=3/7 - correct
P(B|F)=4/7 - false! correct is P(B|A)=4/6=2/3
P(A&B)=3/7 * 4/7=12/49 - false! correct is P(A&B)=3/7 * 2/3=2/7≈0.2857
answer: 0.2857
