Hey there!
To solve this problem, we'll use the slope given two points formula:
y2-y1/x2-x1
Now, we can plug in our values from our points, (-9, 5) and (-8, w). We'll have to set that equal to four, as we know that since that formula gives us slope, if we have slope, we have to set it equal. We have:
w-5/-8-(-9) = 4
w-5/-8+9 = 4
w-5/1 = 4
w-5 = 4
w = 9
Now, to check we can plug 9 back in and have (-9, 5) and (-8, 9). Thus,
9-5/-8-(-9) = 4
4/-8 + 9 = 4
4/1 = 4
4 = 4
Therefore, w equals 9.
Hope this helps!