Illuminations: Comparing Sets
Illuminations (National Council of Teachers of Mathematics)

A children’s book sets the stage for this lesson which encourages students to review counting back. In this lesson, children write subtraction problems and model them with cubes. They compare sets and record differences in the form of a table. The additive identity is reviewed in the context of comparing equal sets.

Illuminations: Counting Back
Illuminations (National Council of Teachers of Mathematics)

Students count back to compare plates of fish-shaped crackers, and then they record the comparison in vertical and horizontal format.