Question: Is there a formal logic symbol for "why"? For example how would you formulate "Why is 2^4 > 4^2?" Could that be formulated in pure symbols of logic if possible?

Also, the phrase "what is" can it be described with logic symbols? Is it just "=" equals? So for example you walk down the street and hear a bang. And you conclude it's either a car crash or a kid popping a balloon. How would that be expressed logically with symbols?

Answer: 
It is not impossible in principle that there might be a logic of explanation, which is to say, a logic that answers "why?" questions. Different logics, such as intuitionistic, relevance, linear, etc., have different natural semantics. It is not unthinkable that one could have a logic whose natural semantics was that of explanation. Asserting a proposition "A" would then be interpreted as "A is explicable", and a conditional "A → B" would be interpreted as "A explains B", or possibly "an explanation of A can be manipulated into an explanation of B". 

The main problem is that I expect it would be fiendishly hard to come up with satisfactory general rules for such a logic. Carl Hempel attempted to describe a logic of scientific explanation, but it is widely regarded as unsuccessful. Different branches of science seem to use different paradigms for explanations of phenomena, so the rules would be difficult to generalize. 

In some specialized contexts one might be more successful. In computer programming, for example, running a debugging tool might be interpreted as enquiring why one obtained a particular result from a program. Depending on how the program is structured, it might be possible to produce debugging output that takes the form of a formal logic.
This sort of thing may have some bearing on answering your question (and won't fit in a comment):

[![enter image description here](https://i.stack.imgur.com/FZjOQ.png)](https://i.stack.imgur.com/FZjOQ.png)
The Oxford Handbook of Epistemology p409

An '[explanandum](https://en.wikipedia.org/wiki/Explanandum_and_explanans)' is what is to be explained