Answer
about $ 88.6\%$
Work Step by Step
Calculating P for x=$80$ (year-olds):
$ P(80)=\displaystyle \frac{90}
{1+271 e^{-0.122(80)}} \approx$88.6140180423
The probability that an 80-year-old
has some coronary heart disease is
about $ 88.6\%$.