A solution to a equation is when the variable is substituted fully. That makes the equation true.
Answer:
a. 1.44
Step-by-step explanation:
We are interested in determining whether or not the proportion of the population in favor of Candidate A is significantly more than 40%.
At the null hypothesis, it is tested if the proportion is of at most 40%, that is:

At the alternative hypothesis, it is tested if the proportion is of more than 40%, that is:

The test statistic is:
In which X is the sample mean,
is the value tested at the null hypothesis,
is the standard deviation and n is the size of the sample.
0.4 is tested at the null hypothesis:
This means that 
A random sample of 200 people was taken. 90 of the people in the sample favored Candidate A.
This means that:

Value of the test statistic:



Thus the correct answer is given by option a.
If sounds travel 335 meters in 1 second , in 1 minute it travels 60 times that distance :
335m × 60 = 20100 meters
Sounds travel 20100 meters per minute
if 1000 meters = 1 km ,
20100 meters = 20100/1000 km
20100 meters = 20.1 Km
Awnser : Sound would travel 20.1 km in one minute