Total numbers of elementary events are 2+ 2 = 4

Let E be the event of getting at least two heads

The favorable outcomes are: HH, HT, TH

Total numbers of favorable outcomes are 3

P (ATLEAST one head) = P (E) = 3/4

Note: at least one head means the outcome with one head or more will be considered favorable and the outcome with no head at all will be ruled out.