1. 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.

2. 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)

3. 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