Justifying steps in an Algebraic Proof?

Question

Conjecture : if 3( x-1) = -27 then x = -8 ,
A: 3(x-1)=-27 =  Given,
B. 3x -3 = -27  _______,
C: 3x = -24  _______,
D: x = -8  ______.
What are the properties for B,C, an D

Answer 1

let G be abelian group , prove that being abelian  is a structural property of G by showing that if G' IS isomorphism to G then G' is abelian also