19. \( (8-\sqrt{-25})-\sqrt{-81} \)

Let's break down the expression step by step! First, we have \( \sqrt{-25} \) and \( \sqrt{-81} \). Since both involve square roots of negative numbers, we can express them using imaginary numbers. We know that \( \sqrt{-25} = 5i \) and \( \sqrt{-81} = 9i \). Now we can substitute these values back into the expression: \[ (8 - \sqrt{-25}) - \sqrt{-81} = (8 - 5i) - 9i \] Combining the imaginary parts gives us: \[ 8 - 5i - 9i = 8 - 14i \] So, the final answer is: \[ \boxed{8 - 14i} \]