I can’t seem to figure this out ...

How to find the slope is by using the formula: y1 - y2 / x1 - x2
-5 - (-6) / -7 - 0 = 1 / -7 = -1/7 as the slope
With the slope you use the y = mx + b and substitution to find the y intercept.
-5 = -1/7(7) + b --) -5 = -1 + b --) -4 = b
-4 is the y-intercept.
The equation is y = -1/7x - 4 and if you substitute -5 = -1/7(7) - 4 --) -5 = -1 - 4 --) -5 = -5 so the equation is correct.