standard_description: Prove that, given a system of two equations in two variables, replacing one equation by the sum of that equation and a multiple of the other produces a system with the same solutions.
problem_activity: Task
A rectangular tank is $24\text{ cm}$ wide, and $30\text{ cm}$ long.  It contains a stone and is filled with water to a height of $8\text{ cm}$.  When Amy pulls the stone out of the tank, the height of the water drops to $6\text{ cm}$.  Find the volume of the stone.
[IMG]


aligns: no