Adding and subtracting tens mentally

Add and subtract a two-digit number and tens mentally and using concrete/pictorial representations

Usually learned at ages 6–7

Builds on: 10 More or 10 Less, The two digits of a two-digit number

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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