To solve the equation \(-6x = 48\) for \(x\), you should divide both sides of the equation by \(-6\). This will isolate \(x\) on one side of the equation.
So, the operation you need to perform is:
\[ \frac{-6x}{-6} = \frac{48}{-6} \]
This simplifies to:
\[ x = -8 \]
Thus, dividing both sides by \(-6\) is the correct step to take.