If unbiased coin then the probability of Head in coin flip when coin is flipped two times $= 75%$.

$$P(H_1 cup H_2) = frac12 + frac12 − frac12 times frac12 = frac34$$

But what is the probability of Head in coin flip when coin is flipped two times if the coin is biased and has a $60%$ chance of heads rather than $50%$?