Salutations!
Probability means occurrence of chance.
You have two sides in a coin: heads and tails.
so when you flip the coin 4 times the probability on getting one tail is
one. If you had to find the probability of 2 tails then the answer would be
.
P = (of one tail) =
It cannot be simplified further, as it is in its simplest form already.
Hope I helped (:
Have a great day!