m= - 1/2
b= 3
To graph, start at your b (y intercept) and mark that number on the y-axis. Then continue to build your line using your slope. To do that, start at your b and go down 1 and over 2. Continue until the end of the plane. Then, since it is a negative slope, work your way up 1 and over 2. Then connect your points to get your line.
Hope that helps!