Article / Updated 03-26-2016
Sixth grade is the first time that Common Core math students start to solve problems using variables and the property of equivalence (specifically, the distributive property).
They typically use variables that closely match the values they represent, so s for side length, v for volume, and so on. They also notice that some expressions — even though they may look quite different — always have the same values as each other, and they explore this property, called equivalence.