What is the probability of a coin landing on heads twice when it is flipped 3 times?

Your question is slightly vague, so I will pose a more defined question: What is the probability of 3 coin tosses resulting in heads exactly twice?

This is a pretty easy question to answer. The three possible (winning) outcomes are:

1. Heads, Heads, Tails.

2. Heads, Tails, Heads.

3. Tails, Heads, Heads.

If we look at the possible combination of other (losing) outcomes, we can easily determine the probability:

4. Heads, Heads, Heads.

5. Tails, Tails, Heads.

6. Tails, Heads, Tails.

7. Heads, Tails, Tails.

8. Tails, Tails, Tails.

This means that to throw heads twice in 3 flips, we have a 3 in 8 chance. This is because there are 3 winning possibilities out of a total of 8 winning and losing possibilities.