Well, since we do not know the line, the basic slope formula is Y = mX + B
So look at the line and see where is crosses the y axis (the vertical) and that is your B in the formula or the "Y-intercept" as an example I will used the number 1. Then on your line pick two points, I will use the points (4,4) and (1,2) as an example. To find your slope take the Ys in those points (the second number) and subtract them 4 - 2 = 2. Then subtract the Xs (the first numbers) 4 - 1 = 3. Lastly, take the 2 and divide it by the 3 (yes it can be a fraction) and that is your slope. So the entire answer with my examples would be Y =
x + 1 with 1 being my y-intercept and 2/3 being my slope