One part out of three. Numerator divided by Denominator of the (as whole), then the portion is two parts out of three(whole): Therefore the difference is 2/3 - 1/3 = 1/3.
Note : whenever parts out of the whole is written except one part, rest are plural of the whole and that's why the plurality is made to the denominator only. And not to the numerator. E.g one fifth, two sevenths etc
Slope intercept form is . The -intercept is -1 so we have . To find , look at the points and . The line goes up 1 and over 4, so the slope, , equals . Thus the full equation is