For this case we must raise the equation according to the given statement.
Let the variable "x" be the unknown number.
So, three times the number is: 
If to that term is added "6" we have:

The sum of both terms is "12", then:

Thus, the equation is: 
Answer:

Would it like.. not be C?? Im guessing its C (:
Answer:
Yes.
Step-by-step explanation:
If you write out the coordinates, you can see that you can do the Vertical Line Test and confirm that if you were to write a function, it would be an actual function. No 2 x-values can be the same y-values. The coordinates all have separate xy values (or the same exact xy values) and you can determine a function.
3= 3 thirds + 3 thirds + 3 thirds = 9 thirds
2/3 = 2 thirds
9 + 2 = 11 thirds. (11/3)