Final answer:
The property being used in the given equation is the associative property of addition.
Step-by-step explanation:
To determine the property being used in the given equation, we can simplify both sides of the equation and compare the results.
Starting with the left side:
(-6.8 + (-5.1)) + 6.2 = -11.9 + 6.2 = -5.7
Now, simplifying the right side:
(-5.1 + (-6.8)) + 6.2 = -11.9 + 6.2 = -5.7
As we can see, the result on both sides of the equation is the same. Therefore, the property being used is the associative property of addition.