Answer : The volume of kristas rock is 30 mL.
Explanation :
From the given image we conclude that:
Initial volume of liquid = 150 mL
Final volume of liquid = 180 mL
Now we have to determine the volume of kristas rock.
Volume of kristas rock = Final volume of liquid - Initial volume of liquid
Volume of kristas rock = 180 mL - 150 mL
Volume of kristas rock = 30 mL
Therefore, the volume of kristas rock is 30 mL.