Why negative integers are not in solution set

Negative numbers aren't in a solution set because in equations and inequalities you have to multiply and divide and a positive number divided by a negative number will be a negative number. Positive divided by positive will be positive. Negative divided by negative will be positive. So that's why negative numbers aren't a solution to any set or equation. 

hope this helps

The answer is c. 7 (i think) i’m almost sure though