Answer:
The answer is 7/30
Step-by-step explanation:
According to counting rules, we use permutation when we want to choose successively and without replacement, as given in this problem
Rule of permutation: nPr = n! /(n-r)!
where: n:objects and r:sample
n of mysteries=9 ; r of mysteries=1 ; ⇒ 9P1
n of biographies=7 ; r of biographies=1 ; ⇒ 7P1
n of total books=9+7=15 ; r of total books=2 ; ⇒15P2
Probability=( 9P1 x 7P1 ) / 15P2 = 49/210 = 7/30
Hope this helps :)
