Is the answer just simply 24?

the answer is 1,

C6+H12+O6=24 molecules

that means you need one of C6, one of H12 and one O6

one of each to make 24 molecules

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.

practical process described pest part of scientific investigation.

because practical knowledge is powerful then therotical knowledge.