Recognize opposite signs of numbers as indicating locations on opposite sides of 0 on the number line; recognize that the opposite of the opposite of a number is the number itself, e.g., –(–3) = 3, and that 0 is its own opposite.
What are opposites and what happens when you add them together? How can you use counters to model 7-9? What about 3 – (-3)? Students work with counters to model adding and subtracting integers.