To find the volume of the solid, take the final water volume - the previously measured volume of water (before you put the solid in)
107. 4 mL - 102.5 mL = 4.9 mL
If it weights 8 g and is 4.9mL, find the g per mL
8 g/4.9 mL = 1.632653061 g/mL = 2 g/mL (sig digits)