Will give ! : )

an employee at a pet shop randomly selects a fish from a tank where there are 5 guppies, 4 platyfishes, and 3 rasboras.

what is the probability that the selected fish is a platyfish?

enter your answer as a fraction, in simplified form, in the box.

There are 12 fish total in the tank, and we are looking for the probability that you will get a platyfish , which there are 4 of. 
So, you take 4, and put it over 12.

       4            1
   =
     12             3
Finally, you'll reduce 4/12 to 1/3. 
So, 1/3 is your answer.