Whats the probability of getting at most one heads when two fair coins are tossed?

When two fair coins are tossed, you have the following possible outcomes:

HH, HT, TH, TT.

So, at most implies that you get either i) zero heads or ii) one head.

From the possible outcomes we see that 3 times we satisify the outcome.

Thus, probability of at most one head is 3/4.