Answer: 3.7 g/mL
Step-by-step explanation:
The volume is the difference of the ending level and the starting level of the water which was:
13.5 mL - 12.0 mL = 1.5 mL
Density is calculated Mass/Volume.
5.5 g / 1.5 mL = 3.66666.. --> 3.7 (using the correct number of significant figures.)