Me! and can you explain how you got that answer ?

The answer x = -3 is correct ; not really any mistakes made but they do seem to skip a step from 8^(-1) to 2^(-3) if that is confusing you.

8 = 2^(3) 
so
(8)^(-1) = (2^3)^(-1) = 2^(3*-1) = 2^(-3)

Distance=slopeslope is -2/4which equals-1/2the distance between these two points is -1/2