If a fair coin is tossed twice, what is the probability of obtaining at least one head?

Mrs Gabriel is pregnant. The probability that she will give birth to a girl is 1/2 and with  blue eyes is 1/4. What is the probability that she will give birth to a girl with blue eyes? 

A coin is thrown 3 times. What is the probability that atleast one head is obtained?

A bag contains 8 red balls and some white balls. If the probability of drawing a white ball is half of the probability of drawing a red ball then find the probability of drawing a red ball and a white ball if the balls are drawn without replacement.

Two dice are tossed. What is the probability that the total score is a prime number.