Hello!
First, let's find the slope. We will need to find our two points, which are (-1,-2) and (3,-4). We divide the difference in the y-values by the difference in the x-values.

Therefore, our slope is -1/2.
Now, we need to find the y-intercept, which, on the graph, appears to be -2.5. Just to check, we will plug a point into the equation and solve for b.
-4=-1/2(3)+b
-4=-1.5+b
b= -2.5
Therefore, our equation is below.
y= -1/2x-2.5
I hope this helps!