Brianna went into a bakery and bought 2 cookies and 3 brownies, costing a total of $9.50. Nevaeh went into the same bakery and bought 10 cookies and 6 brownies, costing a total of $20.50. Write a system of equations that could be used to determine the price of each cookie and the price of each brownie. Define the variables that you use to write the system.

In a test for esp (extrasensory perception), a subject is told that cards only the experimenter can see contain either a star, a circle, a wave, or a square. as the experimenter looks at each of 20 cards in turn, the subject names the shape on the card. a subject who is just guessing has probability 0.25 of guessing correctly on each card. a. the count of correct guesses in 20 cards has a binomial distribution. what are n and p? b. what is the mean number of correct guesses in 20 cards for subjects who are just guessing? c. what is the probability of exactly 5 correct guesses in 20 cards if a subject is just guessing?