Answer:
C. Camille used the subtraction property of equality in step 5.
Explanation:
In step 2, Camille subtracted 80 from both sides of the equation. In step 3, she simplified the equation by combining like terms. In step 4, Camille divided both sides of the equation by 70 to isolate the variable x. In step 5, she subtracted y-80 from both sides of the equation to isolate x. In step 6, Camille simplified the equation by dividing both sides by -1/70. Finally, in step 7, she calculated the value of x.
Therefore, option C is the correct answer.