To solve the equation \( \frac{x}{-5} = -6 \), you can multiply both sides of the equation by \(-5\) to eliminate the fraction.
So, you would multiply both sides by \(-5\):
\[ -5 \cdot \frac{x}{-5} = -5 \cdot (-6) \]
This simplifies to:
\[ x = 30 \]
Thus, the number you should multiply both sides by to solve for the value of \( x \) is \(-5\).