It would be 1n - 12 + 8y.
4n - 3n = 1n
12 + 8y don’t mix so we can leave it.
Therefore: 1n - 12 + 8y
Answer:

And we can find this probability with the complement rule:

Step-by-step explanation:
For this case we define the random variable X ="driving distance for the top 100 golfers on the PGA tour" and we know that:

And for this case the probability density function is given by:

And the cumulative distribution function is given by:

And we want to find this probability:

And we can find this probability with the complement rule:

Answer:
This means that we are 80% confident that the mean of the drive-through service time is between 178.0 seconds and 181.0 seconds. This conclusion was obtained after examined 576 customers. If you want a greater % of confidence you will have to lower the lower bound and increase the upper bound