Step-by-step explanation and Answer:
If a fish starts at -9 meters and changes by -11 meters, it means the fish is going deeper into the water. The new depth of the fish would be -9 - 11 = -20 meters. This is because a negative change in depth means going deeper (or down) while a positive change means going up towards the surface. So, the fish is now 20 meters below the starting reference point.