To solve the equation \(-\frac{x}{2.9} = -3\), we can start by multiplying both sides by \(-1\) to eliminate the negative signs:
\[ \frac{x}{2.9} = 3 \]
Next, we multiply both sides by \(2.9\) to isolate \(x\):
\[ x = 3 \times 2.9 \]
Calculating the multiplication:
\[ x = 8.7 \]
So the solution to the equation is \(8.7\).
Thus, the answer is 8.7.