The answer you are going to be looking for with this question is 16.4. Hope this helps you out a little :)
Answer:
11 years old
Step-by-step explanation:
If four brothers have the average age 6, then the sum of their ages is

years.
Let x years be the age of sister. If four brothers and their sister have the average age 7, then

Multiply this equation by 5:

The sister is 11 years old.
C. The Y value does not change because you are only reflecting over x= lines. After the first, it is (-3.5). Then (7, 5)