P{H1} = 1/10 * 5/6 = 1/12
P{H2} = 1/10 * 1/6 = 1/60
P{H3} = 9/10 * 5/6 = 3/4
P{H4} = 9/10 * 1/6 = 3/20

Тогда 1/12 * 2/7 + 1/60 * 5/14 + 3/4 * 5/14 + 3/20 * 3/7

Во второй задаче пункт в)
P{x <= 3) = P{x=0} + P{x=1} + P{x=2} + P{x=3}