y=-1/2x+4.5
y=mx+b
first do rise over run so it goes down 3 units and to the right 6 units then you simplify 3/6 to the smallest fraction which would be 1/2 and since the line is going down horizontally the slope(1/2) would be negative then you simply see where the line crosses the y-axis and that is the "b"(4.5) for the equation now all you gotta do is plug in the numbers and you get
y=-1/2x+4.5
