What is the y-intercept of the function, represented by the table of the values below?
a) 12
b) 9
c) 3
d) 6

The y-intercept means it has an x value of 0. So right away we know the answer can't be C or D. 

We first need to find the slope of this line:
(y2-y1/x2-x1)
I'm going to use (1,6) and (2,3)
(3-6/2-1)
-3/1 or -3 is our slope

Now using y=mx+b, we can plug in the slope and a point (1,6) to get the y-intercept

6=-3*1+b
6=-3+b
9=b (add 3 to both sides)

So your answer is B