Answer:
0.55% probability that exactly 5 out of the first 13 customers buy a magazine
Step-by-step explanation:
For each customer, there are only two possible outcomes. Either they buy a magazine, or they do not. The probability of a customer buying a magazine is independent of other customers. So we use the binomial probability distribution to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

In which
is the number of different combinations of x objects from a set of n elements, given by the following formula.

And p is the probability of X happening.
10% of his customers buy a magazine
This means that 
What is the probability that exactly 5 out of the first 13 customers buy a magazine?
This is P(X = 5) when n = 13. So


0.55% probability that exactly 5 out of the first 13 customers buy a magazine
The wording "earns 8% interest each year" does not make it clear whether the savings account interest is compounded. (It usually is in real life, but not always in math problems.) The graphical solution shows both simple interest and interest compounded annually.
Simple interest: the balances will both be $2941.18 after 5.88 years.
Compound interest: the balances will both be $3111.06 after 5.74 years.
Answer:
$79.08
Step-by-step explanation:
Find 20% of 65.90. 20% as a decimal is 0.20. Multiply 0.2 and 65.90.
65.90 x 0.20 = 13.18
Add 13.18 to the original price.
13.18 + 65.90 = 79.08