Three unbiased coins are tossed. What is the probability of getting at most two heads ?

Let S be the sample space.
Here n(S)= $23$ = 8
Let E be the event of getting atmost two heads. Then,
n(E) = {(H,T,T), (T,H,T), (T,T,H), (H,H,T), (T,H,H), (H,T,H)}
Required probability = n(E)/n(S) = 6/8 = 3/4.