There is a way to know "with just the straight text" because every math expression has an order of operations that defines the order that each sub-expression gets processed.
Because of those "ordering rules" your example gets processed like this:
In the United States the acronym PEMDAS is a common mnemonic to help remember the order. It stands for Parentheses, Exponents, Multiplication, Division, Addition, Subtraction.
Following that order for your problem { 6a/(2x+8)3+a }, the parentheses must be evaluated first. Since there is nothing inside the parentheses that can be simplified, the "times 3" that is outside the parentheses comes next, which simplifies to this: { 6a/(6x+24)+a }.
I see where I started to go wrong. After I couldn't simply what was in the Parentheses I restarted at the beginning of the expression, basically I did PEDMAS instead of PEMDAS. But how do you determine if it should be :
6a 6a
_____________ or _______________ +a
(6x+24)+a (6x+24)
Because addition and subtraction are always last. So when you do the multiplication and division first, you get "something plus 'a'."
In other words, trying to change the problem to "6a over something" is merely adding to the confusion. If you do it in-line, you get this: { 6a/(6x+24)+a } which clearly does not have "+a" in the divisor.
Math / Science
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HTH,
Dan