First expression
For this expression you have to apply the subtraction property/addition property, this means everithing you add/subtract in one side gives the same result as the operations done in the right side of the = sign.
Second expression
This expression is equal to the first one, except that the terms in the parenthesis were calculated using the distributive propperties of multiplication.
The properties to use are addition/subtraction properties.
Third expression:
Addition property
Fourth expression
Adition propperty
Fifth expression
In this case, since there is only one term on each side, and in the left one the variable is being multiplied by a coefficient, you have to apply the multiplication propperty.
Sixth expression
This expression is reflexive, it means, it tells you what the value of the variable is.