Slope is rise over run which means that the -5 will apply to your y values and the 4 will apply to your x values. This slope would have a point move down 5 units and to the right 4 units to get the location of the next point when going left to right. Because the slope contains a negative, the slope will be angled downward left to right. The negative only applies to the 5.
At first we must keep in mind that two triangles are similar when they have same angle configuration, that is, each pair of angles is congruent. If ABC and DEF, then and . Hence, and .