The slope of a line between two points is (difference between y-coords)/(difference between x-coords)=(5-1)/(1-(-2))=4/3 or (1-5)/(-2-1)=-4/(-3)=4/3. Draw a picture or graph and it will be clearer by simply counting the units in the vertical and horizontal displacements, then the slope is vertical/horizontal or (delta y)/(delta x). If the slope is negative, the line is leaning backwards (\), if positive it's leaning forwards (/), if zero (no difference in the y coords) it's horizontal, and if infinite (no difference in the x coords) it's vertical. In this case, the slope is positive and the line is leaning forward.