To solve the equation \( \frac{x}{-5} = -6 \), you need to eliminate the fraction. You can do this by multiplying both sides of the equation by \(-5\).
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 \( x \) is \(-5\).