Binomial and probability

Twenty percent of the employees of a large company are female. Find the probability that in a random sample of 15 employees, at least two are female?

I have the answer I just don't get how to do it.

Let x = number of females selected

Pr ( at least two are female)

= Pr ( x >= 2)

= 1 - Pr( x =0) - Pr( x =1)

= 1 - 15C0 (.2)^2 (.8)^15 - 15C1 (.2)^1 (.8)^14
= you calculate

Let X be number of females employees of a large company.

p = 0.25
q = 1 - 0.25 = 0.75

n = 15

P(X ≥ 2) = 1 - P(X ≤ 1) = 1 - 0.08018076605 = 0.9198192340, answer!

P(X ≤ 1) = P(X = 0) + P(X = 1) = 0.01336346101 + 0.06681730504 = 0.08018076605

P(X = 0) =

(15)
(0)*(0.25^0)*0.75^15 = 0.01336346101

P(X = 1) =

(15)
(1)*(0.25^1)*0.75^14 = 15*0.25*0.01781794801 = 0.06681730504