Answer :
Probability of getting tails on the first flip: 1/2 (because it's one of two possible outcomes).
Probability of getting tails on two consecutive flips: 1/4 (because it's one out of four possible outcomes- tails tails, tails heads, heads tails, heads heads)
A simpler way of thinking about it is 1/2*1/2, because you already have 1/2 for getting tails the first time, and if getting tails the second time were an independent event then the probability would be 1/3, but since it's getting tails twice you multiply the probabilities.
Either way, the answer is 1/4 (or 25%)