Materials Needed: None

## WhyEdit

What does subtraction of fractions have in common with subtraction of decimals? What do these have in common with subtraction of expressions that contain variables? How is subtraction related to addition?

## Learning ObjectivesEdit

- Explain why when we subtract, we need common denominators or like place values or like terms or common units.
- Solve problems that involve finding changes, differences, or missing pieces.
- Use the commutative property of addition to aid in performing mental subtraction.

## Warm-upEdit

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## ActivityEdit

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