An object with a mass of 3.0 g raises the level of water in a graduated cylinder from 25.1 ml to 33.1 ml. what is the density of the object?

The displaced volume of the water, because of the submersion of the object, is equal to the volume of the object.

So to find the volume of the object we calculate the difference in volume of water:
33.1-25.1 = 8 ml

Since 1 mL of water has the volume of  1cm^3, then the volume of the object is 8 cm^3.

The density of the object is found by the formula:

density= mass/volume= (3 g) / (8 cm^3) = 3/8 (g/cm^3)= 0.375 g/cm^3

0.375 g/cm^3