You can take any 2 points from the table and calculate the slope, as follows:
-2-(-4) 2
m = slope = ---------- = ------ = -1/5
-5 - 5 -10
The slope-intercept form is y = mx + b. You already know m (which is -1/5), and have several points from which to choose to obtain x and y. Let's use the given point (-2, -1).
Then -1 = (-1/5)(-2) + b, or -1 = 2/5 + b. Solve for b.
-5 = 2 + 5b, so 5b = -7, and b = -7/5.
The desired equation is y = (-1/5)x - 7/5.