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 least two heads or at most two tails. So, desired outputs are TTH, THT, HTT, THH, HTH, HHT, HHH

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

Probability of getting at most 2 tails or at least 2 heads

Conclusion: Probability of getting at least two heads or at most two tails is