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Balance chemical equations without trial and error?
Thanks Ben, the other answer was helpful... but is it possible to do it when, say, five variables are involved?
E.g.: $\textrm{Na}_2\textrm{CO}_3 + \textrm{HCl} \to \textrm{NaCl} + \textrm{H}_2\textrm{O} + \textrm{CO}_2$