Answer:
We know that In 1990, the mean duration of long-distance telephone calls originating in one town was 7.2 minutes. And we want to test if the mean duration of long-distance phone calls has changed from the 1990 mean of 7.2 minutes (alternative hypothesis) and the complement rule would represent the null hypothesis.
The correct system of hypothesis are:
Null hypothesis: 
Alternative hypothesis: 
So then the best option for this case would be:
H0: μ = 7.2 minutes Ha: μ ≠ 7.2 minutes
Step-by-step explanation:
We know that In 1990, the mean duration of long-distance telephone calls originating in one town was 7.2 minutes. And we want to test if the mean duration of long-distance phone calls has changed from the 1990 mean of 7.2 minutes (alternative hypothesis) and the complement rule would represent the null hypothesis.
The correct system of hypothesis are:
Null hypothesis: 
Alternative hypothesis: 
So then the best option for this case would be:
H0: μ = 7.2 minutes Ha: μ ≠ 7.2 minutes
And in order to test the hypothesis we can use a one sample t test or z test depending if we know the population deviation or not
Answer:
or 
Step-by-step explanation:
To solve the quadratic equation we must factor the expression
Look for 2 numbers that when you multiply them, obtain the result -100 and when you add them, obtain the result -15.
You can verify that these numbers are -20 and 5

Then the polynomial factors are

The zero product property says that if two terms
then
or 
So
or 
or 
Answer:
B
Step-by-step explanation:
you have to put them a equation
like
example: 2m + 10
hope this help