Here is you're answer:
In order to get you're answer you first need to solve this equation then draw the model.


- Use KCF

- Now solve:

- Simplify:


"Now draw four boxes, then draw another box under each box with 3 parts in each box. Then color 2 parts of each box, Add each box to equal 6 which is you're answer."
Therefore you're answer is "6."
Hope this helps!