Solve exactly. \[ \begin{array}{l} \log _{2}(-x-7)=\log _{2}(8) \\ x= \end{array} \] Next Question

Step 1 ：The given equation is \(\log _{2}(-x-7)=\log _{2}(8)\).

Step 2 ：The equation is in the form of \(\log_a(b) = \log_a(c)\), which implies that \(b = c\). Therefore, we can equate \(-x - 7\) to \(8\) and solve for \(x\).

Step 3 ：Solving the equation \(-x - 7 = 8\) gives \(x = -15\).

Step 4 ：The solution to the equation is \(\boxed{-15}\).