Answer:
A. The subtraction property of equality
Step-by-step explanation:
We have to find the rule applied to obtain line 3 from line 2.
Now, line 2 is -4x + 9 = 2x + 10 and line 3 is -6x + 9 = 10.
We can see that the only possible way to get line 3 from line 2 is by subtracting 2x from both the sides.
i.e. -2x - 4x + 9 = -2x + 2x + 10
i.e. -6x + 9 = 10
Hence, the subtraction property of equality is the justification for getting line 3 from line 2.
