1. Guide students to understand the concept of additive associative law: First, explain to students that additive associative law means that for any three numbers A, B and C, no matter which two numbers are added first, the result is the same as the third number. For example, (a+b)+c=a+(b+c).

2. Demonstrate through concrete examples: provide students with some specific numbers, such as 3, 4 and 5, and let them try to calculate by the law of addition and combination. For example, ask students to calculate the results of (3+4)+5 and 3+(4+5) and compare whether they are equal.

3. Use of exercises: design some exercises for students to calculate on paper or computer. These exercises can include the addition of multiple numbers, so that students can calculate according to the law of addition and combination and check whether their answers are correct.

4. Guide students to discover the law: through observation and summary, guide students to discover the law of addition and association. For example, let students observe several different series, such as (1+2)+3, 1+(2+3) and (1+2)+(3+4), and let them find that the results of these series are the same.

5. Expand application: guide students to apply the additive associative law to practical problems. For example, let students solve some problems related to shopping and distributing goods, and let them use the law of additive combination to calculate.

6. Feedback consolidation: Give students feedback in time, correct their mistakes, and encourage them to continue practicing and applying the law of additive association. Feedback can be oral or written to ensure that students' understanding and application ability of additive associative law can be consolidated and improved.