Take two coordinates, (0, 4) and (1, 5) for example. It's rise over run so y is on top of x. So you would subtract the y's, 5 - 4, and subtract the x's, 1 - 0. That would be 1 over 1, which would just be 1. Then plug in the x and y coordinates; any pair of coordinates will be fine. The equation should look like this, 4 = 1(0) + b. 1 times 0 is 0 so that makes b, the y-intercept, 4, giving you, y = x + 4 as your equation.
