When you are given a point through which a line passes and the slope of that line, you can calculate the equation of that line. The general equation to solve this kind of equations is called as point-slope form. The point slope of a line passing through (a, b) with slope of m is (y - b) = m * (x - a). Now substituting the values in the above equation you can obtain the equation of the line in terms of x and y. In case you are given with two points first find the slope of the line which is the ratio of difference of y coordinates to the difference of the x coordinates and substitute it in the above equation using any one of the points. This video shows how to find the equation of a line in point slope form.