The numbers '4' and '8' and the words 'four' and 'eight' in your example are already abstract symbols. In fact most words in natural languages are symbols/pointers to different things or processes in the human experience.
Of course you can argue that the 4 number, is more abstract than the word, and that the variable x is more abstract, than the 'concrete' number 4 ... even so, you can build arbitrary complex structures with just 1 level of abstraction/indirection.
In this sence, I agree with scoofy: '(usage of) natural language IS symbolic reasoning' indeed.
It's trivial to define a mapping from the symbolic to the rhetorical. The reverse isn't trivial, but even if it were trivial, we'd still prefer the symbolic.
4 + 4 = 8.
Let there be a function f taking one argument, returning a result that is the argument multiplied by two.
f x = x * 2
Do you see the difference between rhetoric and symbol? The point is, perhaps, more literal than you suspected?