We know that,

Probability of occurrence of an event

Let T be tails and H be heads

Total possible outcomes = TTT, TTH, THT, HTT, THH, HTH, HHT, HHH

Desired outcomes are at most two tails. So, desired outputs are THH, HTH, HHT, TTH, THT, HTT, HHH

Total no.of outcomes are 8 and desired outcomes are 7

Therefore, the probability of getting at most 2 tails

Conclusion: Probability of getting at most two tails is