Explanation:
Step 2: -2x - 3 = x - 18
In order to go to Step 3, we must remove the -2x term from the left. In order to do this, we add 2x on both sides:
-2x - 3 + (2x) = x - 18 + (2x)
=> Step 3: -3 = 3x - 18.
Hence the answer is Addition Property of Equality. (A)