Question

how do you find the probability of question a,b&c ?

Answer 1

p(3 or more heads) = p(3 or 4 heads) = 4/16 + 1/16 = 5/16

p(at most 2 heads) = p(0 or 1 or 2) = 1/16 + 4/16 + 6/16 = 11/16