The first compound indequality is:
We can view this in the real line:
There is no number that can be both greater AND less than 7, which makes the correct answer "No solution".
The second is:
Now, we are not looking for intercetion, we are looking for the union of both. The firts inequality takes all number less than 7 and the second all that are greater than 7, so the only one that is not a solution is 7, which means the correct answer is "all real numbers except 7"
The third is:
This is the same as the first one, but now the 7 is included in both:
So, there is only 7 that can be in both indequalitys, thus the correct answer is "one solution, 7".
The fourth is
This is similar to the second, but now 7 is included, which means it is also a solution, thus the answer is "all real numbers".