4/7 = 8/14 = 12/21 = 16/28, etc
Part A:
-np - 70 < 40
+70
-np < 110
-n < 110/p
Part B
4w-7k=28
-7k=28-4w
7k=4w-28
k=4/7w-4
Since your second pick is affected by your first pick & your third pick is affected by the first two, it is dependent.
First pick: 18 marbles, 3 are red, so odds are 3/18 = 1/6
Second pick: 17 marbles, 8 are blue, odds are 8/17
Third pick: 16 marbles, 7 are black, odds are 7/16
<span>1/6 * 8/17 * 7/16 = 56/1632 = 7/204 & as mentioned before it's dependent</span>
