Use the slope formula, which is y2-y1 divided by x2-x1. (0,1) is the first pair of points, so it will be x1 and y1. (3,0) will be the 2nd pair of points, so x2 and y2. Plug in the numbers into the formula, so 0-1 divided by 3-0 is -1/3 which is the slope.