y = (-1/2)x - 5 is a straight line. It has a slope of -1/2 which means for every 1 down on the y axis it goes 2 over on the x axis.
1. Pick two different x values, for example 1 and 2. Plug them in to determine corresponding y values. Plot the two points (x,y). Draw a line through them.
2. From the equation, we know -5 is the x intercept. (0,-5) is a point on the line. Go one down and two over. This is a second point on the line (2,-6). Connect them to plot the line.