To find the slope of a line from the graph; m = (y2 - y1) / (x2 - x1), such that (x1, y1) and (x2, y2) are any two points on the line. To find the slope from the equation of the line; you have to put the equation in that form --> y = mx + b, such that m is the slope.
You can find the slope of a straight line by dividing the difference of the Y-coordinates of a point on a line by the difference of the X-coordinates. For example, if a straight line through the points (4, 3) and (1, 2), you can find its slope as:
(Y2 ? y1)/ (x2 ? x1)
3-2/4-1 = 1/3. Learn more through http://www.ehow.com/how_4661192_slope-line.html.