Questions 13 and 17 if anybody knows ?

13) If T(n) = 2n-7, what is the 5th term?
n is the number of the term you are looking for. In this instance, n is equal to 5.

T(5) = 2(5) - 7
T(5) = 10 -7
T(5) = 3

The 5th term is 3.

17) inequality based on the line number.
Since the line does not extend in any direction outward. It means that the range should be within -3 and 3. 
Solid circle means that -3 is equivalent to x
hollow ciccle means that 3 is not x.

-3 < x < 3

x = any number from -3 upto 2.