According to the question, three coins are tossed together.
By using the formula of probability, we get,
P (E) = favourable outcomes / total possible outcomes
Total number of possible outcomes is $2^3=8$
Let E be the event of getting at least one head and one tail
E = {(H, T, T) (T, H, T) (T, T, H) (H, H, T) (H, T, H) (T, H, H)}
n (E) = 6
P (E) = n (E) / n (S)
= 6 / 8
= 3/4