1. The problem is to simplify the expression $$-54 - (-54)$$. 2. Recall that subtracting a negative number is the same as adding its positive counterpart, i.e., $$-(-54) = +54$$. 3. Therefore, the expression becomes $$-54 + 54$$. 4. Adding these together, $$-54 + 54 = 0$$. Final answer: $$0$$.