Probability - General Questions

4 unbiased coins are tossed together. What is the probability of getting at least one head?

A bag contains 8 red, 8 blue and 2 green balls. Two balls are drawn at random. What is the probability that both are red?

A number is chosen at random from 1 to 20. What is the probability that it is a multiple of 6?

A letter is chosen at random from the word 'SCIENCE'. What is the probability that it is a vowel?

A bag contains 7 red, 6 blue and 1 green ball. Two balls are drawn at random. What is the probability that both are red?