Answer:
- given
- distributive property
- commutative property
- collect terms
Step-by-step explanation:
On the first line, the expression shown is the one on the left side of the problem statement. It is "given." This is often the case in problems of this type.
On the second line, parentheses are gone. The distributive property tells you how to remove them.
On the third line, the middle two terms have traded places. The commutative property of addition lets you do that.
On the last line, like terms are combined. We call that operation "collect terms." (It is a combination of many others, including use of the distributive property to factor the variable from like terms, adding two numbers to get their sum, and substituting the sum for the two numbers.) You might want to refer to an example from your text to see exactly how this is justified.
