For Part A, the model that best represents the story is:
A bar diagram is divided in half, with 2 connecting cubes on one side and 4 on the other side. A line stretching across the entire diagram is labeled 6.
This model shows that Justin starts with 6 blocks, gives away 2 (the cubes on one side), and has 4 blocks left (the cubes on the other side).
For Part B, the equation that shows the story is:
6 - 2 = 4
This equation represents Justin starting with 6 blocks, giving away 2, and having 4 blocks left.