When three unbiased coins are tossed, there are 2^3 = 8 possible outcomes, since each coin can either be heads or tails.
The possible outcomes are:
Out of these eight possible outcomes, there are three outcomes where we get at most two heads: HHT, HTH, and THH. This is because in these outcomes, there are either one or two heads, and in the other five outcomes there are three tails.
Therefore, the probability of getting at most two heads is 3/8, or 0.375, since there are three favorable outcomes out of eight possible outcomes.