Equation of a line:

m = gradient: The difference between two y points and two x points.

c = y-intercept: Where the line crosses the y-axis (x=0)
You have:

so you are missing the m and the c.
To calculate m find two y coordinates -you have (12,
7) and (0,
1)- and subtract them. Then divide this by the subtracted values of the x coordinates -you have (
12, 7) and (
0, 1)- This gives:



To calculate the c, you just see where the line crosses the y-axis. Because you have the point (0, 1), you know that when x=0, y=1. Because x=0 is on the y-axis, you can tell that the line passes through y=1. This makes your c = 1:

When you plug these values into the equation you get your answer:
