Answer:
Step-by-step explanation:
In order to write the equation of this line, we need to pick 2 points on the graph where the line goes right through the intersection of the grids. Actually, you only need 1 of these, because the line goes through at (0, 15). Another point then can be (6, 6). Locate this point so you know what I means when I say that the line goes right through where the grids intersect at x = 6 and y = 6 (as opposed to somewhere in the middle of one of these grids). Find the slope between these 2 points:

Since there's only one choice with that slope, that is the choice you want.
I think im not completely sure but it might be -3
Expression: 2n - 1
When n = 7
2n - 1 = 2(7) = 1 = 14 - 1 = 13