start with -x = 15
multiply both sides of the equation by -1 to get:
x = -15.
that's your solution.
confirm by replacing x with -15 to get:
-(-15) = 15 which results in 15 = 15 which confirms the solution is correct.
i don't know where -1/15 comes from.
that doesn't seem to figure in the problem.
bottom line is you got it right but the steps that you took to get the answer don't look right.