Answer:
110 test
Step-by-step explanation:
Let
x ----> the number of packet of 10 test
y ----> the total cost
we know that
The number of packet of 10 test purchase multiplied by $11 plus the enrollment fee of $30 must be equal to $151
so
The linear equation that represent this scenario is

we have

substitute

Solve for x
subtract 30 both sides


Divide by 11 both sides

The number of packets purchase was 11
To find out the number of test, multiply the number of packets by 10

The mean of the discrete probability distribution is of 1.28.
<h3>What is the mean of a discrete distribution?</h3>
The expected value of a discrete distribution is given by the <u>sum of each outcome multiplied by it's respective probability</u>.
Then, considering the given distribution, the mean is given by:
E(X) = 0(0.13) + 1(0.61) + 2(0.15) + 3(0.07) + 4(0.04) = 1.28.
More can be learned about the mean of a discrete probability distribution at brainly.com/question/24855677
So basically the x will want to be singled out and 3/2-y=the variable