Even though tetanus is rare in the United States, it is fatal 70% of the time. If three persons contract tetanus during one year, what

is the probability that none of the three will die.

Assume that fatalities due to tetanus are independent of each other.

If they are independent then the multiplication rule applies.
P(x)*P(y)*P(z)= probability all 3 events happen.
The probability for each is 1 - .7 = .3