Addition and subtraction within 20

Add and subtract within 20 using strategies such as making ten, decomposing a number leading to ten, and using known facts

Usually learned at ages 6–7

Builds on: Number bonds to 9, Fluent adding and subtracting within 10

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On the map from: Marble Skill Taxonomy (v1), © Generative Spark, Inc. (withmarble.com), text CC BY-SA 4.0, database ODbL 1.0: https://github.com/withmarbleapp/os-taxonomy