A dolphin is 30 feet below the surface of the water. She rises 23 feet, sinks 17 feet and finally rises another 27 feet. If there are no other changes, the dolphin is:

• 3 feet above the surface of the water

• 3 feet below the surface of the water

• 63 feet above the surface of the water

• 63 feet below the surface of the water

• negative because both y and z are negative.

• negative because z is further from 0 than y.

• positive because both y and z are negative.

• positive because y is closer to 0 than z.

Using the key as a guide, what is the result of the operation in the model below?

• −13

• −5

• 5

• 13

Which number sentence is represented by the model below?