Given:
The steps of simplification of the expression.

To find:
The properties to justify the line 2 and line 3.
Solution:
We have,

Line 1:
(Rearranging the terms)
Line 2:
(Combining the constant terms)
Line 3:
(Additive inverse property)
Line 4:
(Additive identity property)
Therefore, the justifications of Line 2 and Line 3 are combining the constant terms and additive inverse property respectively.