A bag contains 77 coins consisting of quarters and nickels. The total value of the coins is $12.50. Write a system of equations that can be used to determine the number of quarters, x, and the number of nickels, y, in the bag. a
x + y = 77
0.25x + 0.5y = 12.5

b
0.25x +0.5 y = 77
x + y = 12.5

c
x + y = 77
0.25x + 0.05y = 12.5

d
0.25x + 0.05y =77
x + y = 12.5

yes yes yes yes yes yes yes yes yes

4a. is 3 miles every hour

4b. is 1/3 of an hour per mile

step-by-step explanation:

in counting the number of heads in 4 coin flips, the probability that we get exactly one head is the probability that we get anyone of the following 4 outcomes: httt, thtt, ttht, or ttth. each has probability 1/16, so the probability to get exactly one head in 4 flips is 1/16 + 1/16 + 1/16 + 1/16 = 4/16 = 1/4.