To complete this number sentence so that it illustrates the identity property of addition, we need to remember that the identity property of addition states that adding zero to any number will result in the same number.

The sentence provided is: [ \text{[ ]} = 33 + \text{[ ]} ]

To make this correct and illustrate the identity property:

• The box on the left should contain 33 (the result).
• The box on the right should contain 0, since $33 + 0 = 33$.

So, the answer is:

• Left box: 33
• Right box: 0

Would you like further details on the identity property of addition, or do you have any other questions?

Here are some related questions you might find helpful:

1. What is the identity property of multiplication?
2. How is the identity property used in algebra?
3. Why is zero considered the "identity" for addition?
4. Can you give examples of the identity property in real-life scenarios?
5. What are other properties of addition and multiplication?

Tip: Remember, the identity property keeps the original number unchanged when combined with the "identity" element (0 for addition, 1 for multiplication).