Answer
(a)$p(x>20)\approx0$
(b)$p(x<5)=0.2137$
Work Step by Step
Given that n=25, p=0.25, then,
$p(X=x)=\frac{25!}{x!(25-x)!}(0.25)^{x}(0.75)^{25-x}, x=0,1,2,...,25$
(a)$p(x>20)=p(x=21)+p(x=22)+p(x=23)+p(x=24)+p(x=25)\approx0$
(b)$p(x<5)=p(x=0)+p(x=1)+p(x=2)+p(x=3)+p(x=4)=0.2137$
