code:

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a+(bcd) -> (bcd)+a  : does not matter what ops are inside as
                      + is low precedence
 
a-(bcd) -> nothing! : What kind of expression would you need
                      inside parens to get 24 by subtracting
                      to 0..9?? Yes, I know that 0-(-something)
                      will be positive, but we can't have another
                      negative number inside the parens!!!
{edit} Actually, we can, but it does not create a solution! {/edit}
{edit} And it can be rewritten as not to need the parens! {/edit}
 
a/(bcd) -> nothing! : Again, what kind of number would we need
                      inside parens to get 24? A very small number!
                      In order to be so, we'd need something like
                      a/(b/c/d) because a/(b+c/d) or a/(b/c+d) would
                      not give a number below 1 unless the added item
                      was 0 and even then it would not be "small enough"
                      to get 24... (hope you're still following me!)
                      If we did not use a / inside the parens, then
                      the number would not be between 0 and 1 and so,
                      dividing a number from 1 to 9 by it would not
                      yield the needed result! Finally, a/(b/c/d) can
                      be simplified as a/b/c/d !!!
 
a*(bcd) -> (bcd)*a  : We will arrive at this test case sooner or later!
                      So, no need to handle it in here.
 
Please check my assumptions, but I do believe that a(bcd) can be safely
left out of the game as we're not trying to get ALL solutions but just
ONE!

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