When students are multiplying mixed numbers they generally get an improper fraction as their product. This improper fraction will need to be converted to a mixed number number. Strategies involve making as many wholes as you can, and then adding the left over unit fractions.
Below is an example of ways that you may see your child thinking about his work. Even if the work your child is doing does not look exactly like this, you will see aspects of this example in your child’s work. The 3, 6, 9 on the bottom are keeping track of how many thirds your have. Notice that the 12 is crossed out. This step shows that 12 thirds is more than we have, so we have 3 wholes and now need to find how many more thirds we have left over.