Question 1164283
use normal approximation
mean is np=100*0.80=80
variance is np(1-p)=80*0.2=16
sd is sqrt(16)=4
the approximate probability would be z<=(x+0.5-mean)/sd=(86.5-80)/4=1.625. The +0.5 is the continuity correction factor.
that probability is 0.9479

The exact probability is 0.9531.