Final answer:
Using a smaller amount of water would result in a more concentrated NaCl solution and a higher calculated percentage of NaCl in the sample.
Step-by-step explanation:
If the amount of water used for the extraction of NaCl from the mixture is decreased from 50 mL to 10 mL, it would result in a more concentrated NaCl solution. This is because there would be a higher amount of NaCl dissolved in a smaller volume of water. As a result, the calculated percentage of NaCl in the sample would be higher.