Well there is a 0.3 chance they won't be cured. (Assuming this is mutually exclusive and they are either cured or not cured)

The chance thatnpatients will be cured is given by

In part d) n = 3 because fewer than 4 means 0,1,2 or 3

In part e) n = 7

The 12-n comes from the total minus the number that are cured