Q:

Numeric error in Excel with parentheses?

I have been able to produce a very simple and challenging numeric calculation error in Excel, am curious as to the reason and perhaps a solution to it:
    |  A      | B                |
----------------------------------
 1  |  X      | 693.702          |
----------------------------------
 2  |  Y      | 693.702          |
----------------------------------
 3  |  Y - X  | 0.0000000000E0   |
----------------------------------
 4  | (Y - X) | 1.1368683772E-13 |
----------------------------------

Essentially in the above, B1 and B2 contain the same value, B3 contains the difference =B2-B1 and B4 contains the same in parentheses (B2-B1). The value returned is significantly different.

A:

I can not replicate this but it looks like you're just hitting the floating point precision of  your version of Excel. One reason for me not being able to replicate is if your values X and Y are the results of some other calculation.
This is nothing to worry about but can be annoying. (I say nothing to worry about since the difference from the correct result is infinitesimal, 0.00000000000011368...) 
Similar example
Microsoft KB article

