I can't seem to get the right answer for the these two questions when solving (Without using Excel):

It is known that 70% of the customers in a sporting goods store purchase a pair of running shoes. A random sample of 25 customers is selected. Assume that customers' purchases are made independently, and let x represent number of customers who purchase running shoes.

What is the probability that at least 17 customers purchase running shoes? (Answer is supposed to be 0.67693)

What is the probability that between 17 and 21 customers, inclusively, purchase running shoes?

(Answer is supposed to be 0.64369)