Mark tosses a coin 25 times. What is the probability that it lands on heads exactly seven times?

1.43%

Step-by-step explanation:

we have that we can solve it by means of binomial, in this case m = 25. Also the probability of head is 50%. we need to know when it falls 7 times, therefore x = 7

the formula is:

P (x) = mCx * p ^ x * q ^ (m-x)

we know that p is 0.5 therefore q is equal to 0.5, replacing:

P (7) = 25C7 * 0.5 ^ 7 * 0.5 ^ (25-7)

P (7) = 25! / (7! * (25-7)!) * 0.5 ^ 7 * 0.5 ^ (25-7)

P = 0.0143

that is, the probability is 1.43%

marco saved more.   he saved $35 more.

step-by-step explanation:

1+2+3+4+5+6+7+8+9+10 = 55

2*10 = 20

55-20 = 35

8(-10x+3.5y-7)

8×-10x + 8×3.5y + 8×-7

-80x + 28y - 56

therefore

-80x+28y-56 is the correct answer