How do you work out the gradient of a straight line?

Look at the graph for two points that you can read the x and y values for easily. Then draw a triangle using these two points and use a ruler to draw a dotted line or just to help you read the x and y values of both of your points. Mark the point with the highest y value as point A and the other point as point B. Your A point has your x1 and y1 values and point B has your x2 and y2 values. To work out the gradient just do (y1 minus y2) and divide this value by (x1 minus x2) and you should end up with your gradient.