step 1
Find out the equation of the line
y=mx+b
we have
m=1/3
point (-1,-2)
substitute the given values and solve for b
-2=(1/3)(-1)+b
-2=-(1/3)+b
b=-2+1/3
b=-5/3
therefore
y=(1/3)x-5/3
step 2
To graph a line we need at least two points
so
Assume a value of x and find out the value of y
For x=-4
y=(1/3)(-4)-5/3=-3
First point (-4,-3)
For x=7
y=(1/3)(-7)-5/3=-4
Second point is (-7,-4)
step 3
Plot the given points, and join them to graph the line
see the attached figure to better understand the problem