Answer:
1). A. Add/subtract a quantity to/from only one side
2) B. No
Explanation:
Given equation A
5x-2+x = x-4
Given equation B
5x+x = x-4
We can see that the difference between equation A and B is the 2 that subtracted from the left hand sides of the equation A. All other functions and constants remains the same.
For us to be able to get equation B from A, we need to simply add 2 to the left hand side of equation A to cancel out the -2 that is there as shown:
From equation A:

Add 2 to the left hand side of the equation

Simplify

We can see that the resulting function gives the equation B
Hence the option B is correct i.e Add/subtract a quantity to/from only one side
Let us find the solution to equation A and B
For equation A:

For equation B:

Since we got different solution for x in both equation, hence both equation are not equivalent.