Answer:
1 minute and 30 sec
Step-by-step explanation:
because there are 60 seconds in a minute and 60+30 is 90
Let
denote the number of packages brought by customer
. If, for instance,
customers are in line, then the total number of packages is
, and

since the number of packages brought by any customer is independent from the number of packages brought by any other.
a.
is the probability that a total of 3 packages are waiting to get wrapped from among a total of 3 customers. This means each customer must have exactly one package. So

b.
is the probability that a total of 11 packages are brought by 4 customers. The only way for there to be 11 packages is if 3 customers bring 3 packages and the last 1 brings 2. There are
ways this can happen, so

Answer:

Step-by-step explanation:
This problem requires subtraction, then division.. The first step is to add 9.5 to each side of the inequality. This isolates 6x on one side and makes the equation easier to understand:

Next, you need to divide each side by 6 to get your answer:

As a little bonus tip, if you ever end up dividing each side by a negative number, you MUST reverse the sign.