In an addition equation, you are often asked to find the sum. It can look like this.

What is the sum? \(3 + 5 = \)

The correct answer is \(8.\) So, the whole addition sentence is \(3 + 5 = 8.\)

Here is another way to ask that question. What number is missing? \(3 + 5 = \square.\)

There should be an \(8\) in the box.

We can change the question by making a different missing number.

What number is missing? \(\square + 5 = 8.\)

Now the correct answer is \(3\) because there should be a \(3\) in the box.

Here is another question. What number is missing? \(3 + \square = 8.\)

Now the \(5\) is missing. The correct answer is \(5.\)