To solve for \( p \) in the equation
\[ -3p = 291, \]
you need to isolate \( p \). You can do this by dividing both sides of the equation by -3:
\[ p = \frac{291}{-3}. \]
Calculating the right side gives:
\[ p = -97. \]
Thus, the solution is
\[ p = -97. \]