Answer:
a. The average number of hashtags used in a social media post from a marketing agency is different than 7 hashtags.
Step-by-step explanation:
A social media platform states that a social media post from a marketing agency has 7 hashtags, on average.
This means that at the null hypothesis, we test if the mean is 7, that is:

A digital marketing specialist studying social media advertising believes the average number of hashtags used in a post from a marketing agency is different than the number stated by the social media platform.
Keyword is different, so at the null hypothesis, we test if the mean is different of 7, that is:

Thus, the correct answer is given by option a.
Answer
The answer and procedures of the exercise are attached in the following archives.
Step-by-step explanation:
You will find the procedures, formulas or necessary explanations in the archive attached below. If you have any question ask and I will aclare your doubts kindly.
I will attached the picture of what you are talking about here. The answer for this problem is: Yes, that they are congruent by SAS. Meaning that the triangles are congruent if their included angles and any pair of corresponding sides are equal in both triangles. In this case, the sides are both 21 cm and this will make the angle equal for both triangles, so that is why they are congruent.
1.) 8,281 people/km²
2.)
3.) 1226.88 grams
4.) 999.74 grams
5.) 6
I am not sure about number 2.