Answer:
C. Division Property of Equality
Explanation:
In order to recieve your answer for this problem you should cancel out x by dividing both sides by x. This is what it will look like:
7x=84
x=84/7
Final Answer: x=12
Notice how they used Divsion. Therefore "Division Property of Equality."
Please let me know if this helps and if the answer is correct! I hope this clears up some confusion of yours!!