<u>Answer:</u> The density of the quartz is 2.68 g/mL
<u>Explanation:</u>
We are given:
Volume of graduated cylinder = 50.3 mL
Volume of quartz + graduated cylinder = 64.8 mL
Volume of quartz = [64.8 - 50.3] mL = 14.5 mL
To calculate the density of substance, we use the equation:

Mass of quartz = 38.9 g
Volume of quartz = 14.5 mL
Putting values in above equation, we get:

Hence, the density of the quartz is 2.68 g/mL