Which step could you use to start solving the system of equations below?* x + y = 3
-3x – 2y = -7
A. Multiply x + y = 3 by 3 and add it to -3x - 2y = -7
B. Multiply -3x-2y = -7 by 2 and subtract it from x + y = 3
C. Add x + y = 3 to -3x - 2y = -7
D. Subtract x + y = 3 from -3x - 2y = -7

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?