21% adults favor the use of unmanned drones by police agencies. Twelve U. S. adults are randomly selected. Find the probability that the number of U. S. adults who favor the use of unmanned drones by police agencies is (a) exactly three, (b) at least four, (c) less than eight

a)

b)

And we can find the individual probabilities:

And replacing we got:

c)

And replacing we got:

Step-by-step explanation:

Let X the random variable of interest "number of US adults who favor the use of unmanned drones", on this case we now that:

The probability mass function for the Binomial distribution is given as:

Where (nCx) means combinatory and it's given by this formula:

Part a

Part b

We want to find this probability:

And we can use the complement rule and we got:

And we can find the individual probabilities:

And replacing we got:

Part c

We want this probability:

And using the complement rule got:

And we have this:

And replacing we got:

answer:

it is general formula that is used to write value to its excet position

a11 a12 a13

a21 a22 a23

it is the example of order 2 by 3 matrix in this

a11 means value occur in 1 st row 1st column

a12 means value occurs in 1st row 2nd column

a13 means value occur in 1st row and 3rd column

a21 means value occurs in 2nd row and 1st column

a22 means value occurs in 2nd row and in 2nd column

a23 means value occurs in 2nd row and in 3rd column