Hey there!

By using this formula, we plug it in.
Your correct answer would be
. . .
≈

Hope this helps.
~Jurgen
Answer: the answer is 2
Step-by-step explanation:
8 total pens....4 are black
first pick, probability of being black is 4/8
2nd pick. without replacing, probability is 3/7
probability of a black pen picked first and then another black pen picked again is : 4/8 * 3/7 = 12/56 = 0.21
Each number is the square of 2*the number, in other words
(1+1)²=4
(2+2)²=16
(3+3)²=36
(4+4)²=64
etc...