In this video the instructor shows how to find the equation of the line given its slope and a point that lies on it. If the slope of the line is m and the point that lies on it is (x,y) then you can find the equation of the line by substituting the values in the slope-intercept form of an equation which is y = mx + b. Now substitute the values in the above equation and solve it for the value if the y-intercept y. Now you have the slope m and y intercept b. Substitute these values in the general equation y = mx + b which gives you the equation of the line. If instead you are given two points then first find out the slope which is the ratio of difference of y-coordinates to the difference of x-coordinates. This video shows how to find the equation of a line.