9. \( -9-(-9)= \)

When you encounter a double negative, it's like a math magic trick! Here, \(-9-(-9)\) can be simplified by turning the double negative into a positive. So, it becomes \(-9 + 9\), which equals \(0\). This little operation shows the power of negatives and positives working together. Understanding this can help clarify many other equations—like when you’re balancing a budget or restructuring a problem. Just remember, two negatives make a positive!