Answer:
2. given
5. substitution
Explanation:
that the perimeter is 12 is simply a given fact. in the same way as the shape of the object is defined as square.
nothing was calculated, this information is simply there at the beginning, is "given" to us.
step 5 simply takes step 3 and substitutes all sides by the same side, as (per definition) all sides in a square are equal. so, every side can stand in for every other side.