The most important concept in algebra is the "statement of equality" sign. We normally call this an "equal sign". There are two sides to an algebraic equation and the equal sign divides the equation into a left side and a right side.
For this equation
2X - 4 = 8
rather than thinking "2X minus 4 equals 8",
think "2X minus 4 IS THE SAME THING AS 8"
And, by the way, if they are the SAME THING, then if someone performs an operation on one side of that equal sign and does not do it on the other side, then they are no longer the SAME THING. That is to say, if
2X - 4 = 8
then 2X - 2 does NOT equal 8 ,
because something was done to the left side of the equal sign without doing it to the right side. That "something" was adding 2 to the left side and not adding 2 to the right side.
And, by the way, if they are the SAME THING, then if the SAME OPERATION is performed to both sides, then they are still the same.
Repeating this sentence with the word "equal", rather than SAME THING,
And, by the way, if they are EQUAL, then if the SAME OPERATION is performed to both sides, then they are still EQUAL.