The slope is -1/4, which is -0.25x. We know that we are exactly 8 units to the left of the y axis, so we can use the slope to determine the change within the coordinates as the line moves across the graph. The slope has a rise of -1 and a run of 4, meaning every 4 units to the right will be 1 unit up. We must move 8 units to the right, which in turn moves the graph down 8 quarter units. 8 x (1/4) is 2, so we know that the graph has moved down 2 units. (Down because the graph has a negative slope). (-8,3)->(0,1). From this coordinate, we can see the y intercept is 1. Since y=mx+b, we can write y=-1/4x+1. This is your equation. (Sorry for the length, wanted to be thorough)
