Your backpack contains 3 blue pens and 2 black pens. You randomly choose one pen to give to a friend and then you randomly choose another pen to use yourself. What is the probability that both pens are blue

Since there are 5 pens total, and three of those pens are blue, the probability for both pens being blue is 3/5.

(just like if the black pens were being chose the probability would be 2/5, since there are 5 pens total and 2 black pens.)