 Lesson 2-2 Example 3 2-2 Use the Commutative and/or Associative Properties to find the sum mentally. 9 + 13 + 7 Step 1 Look for two numbers whose sum is.

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Lesson 2-2 Example 3 2-2 Use the Commutative and/or Associative Properties to find the sum mentally. 9 + 13 + 7 Step 1 Look for two numbers whose sum is 10, 20, 30, or another multiple of 10. The sum of 13 and 7 is a multiple of 10, 20.

Lesson 2-2 Example 3 2-2 Use the Commutative and/or Associative Properties to find the sum mentally. 9 + 13 + 7 Step 2 Rewrite the expression using the Associative Property. 9 + 13 + 7 = 9 + (13 + 7)

Lesson 2-2 Example 3 2-2 Use the Commutative and/or Associative Properties to find the sum mentally. 9 + 13 + 7 Step 3 Find the sum. 9 + (13 + 7) = 9 + 20 or 29

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