(Don't report the other guy, he needs points and I'll give you the answer)
The rock displaces 1800cm cubed of water -> The volume of it is 1800cm3
To calculate the volume of a right rectangular prism, we take width x length x height.
=> 10 x 12 x height = 1800
So, the height of the rock is 1800 : 120 = 15.
