Answer:
7.17 g/mL
Step-by-step explanation:
Density = Mass / Volume
Given mass of object : 80.4g
We are not given the objects volume, however we are given that when put inside of a container with 20.0mL water, the level of the water rises to 31.2 mL.
31.2 - 20 = 11.2
The water level rose 11.2 mL when the object was placed inside of the cylinder containing the water therefore the object has a volume of 11.2mL
Now to find it's density
recall that density = mass / volume
mass = 80.4 and volume = 11.2mL
so density = 80.4/11.2 = 7.17 g/mL