Assess educators' ability to analyze and compare young learners' decomposition and recomposition strategies for numbers to 20 using manipulatives and visual models. Tasks include interpreting ten-frame, part–part–whole, number-line, and base‑ten representations; evaluating strategy efficiency and developmental appropriateness; diagnosing misconceptions and errors; justifying reasoning and solution paths; and recommending targeted instructional moves to deepen conceptual understanding and fluency.