All of my friends like fruit. 9 friends like bananas, 8 friends like oranges, and 7 friends like plums. 5 friends like both bananas and oranges, 3 friends like both bananas and plums, 4 friends like both oranges and plums, and 2 friends like bananas, oranges and plums. How many friends do I have?

you have 38 friends

Step-by-step explanation:

because you have to add I think so

the answer   is 200

step-by-step explanation:

this is a problem about poisson probabilities.   i don't know if you've

already studied poisson distributions, or if you have a place to look

to read more about the subject.  

here's how you can see a poisson distribution coming.   when there are

a lot of events that may happen at any time (or any place), and when

you're counting how many of them happen at a particular time (or a

particular place), and each event is independent of the others, then

the result is a poisson distribution.   this is roughly true for the

chocolate chips; one chip being in a cookie has only a small effect on

the probability that another chip will be in the cookie.

once you know you have a poisson distribution, you know a lot.   there

is only one parameter to a poisson distribution, so if you know the

mean, you know everything.   the form of the distribution is

  probability of n chips = {[e^(-x)]*(x^n)} / (n! )