Verified answer

if  3 coins are tossed the number of possible appearances

  are      2³   =   8

 they are:    HHH - HHT-THH - TTH - HTT- HTH -THT -TTT  

   you can see there are at least 4 occasions of 2 heads appearing

 ∴ the probability of at least 2 heads appearing  is   4/8  = 1/2