1.OA.B.4
Understand the relationship between addition and subtraction by representing subtraction as an unknown-addend problem. For example, to solve 10 – 8 = __, a student can use 8 + __ = 10.
Khan Academy ResourcesAdd within 20Subtract within 20Subtract within 20 visuallyAdd & subtract within 20Add within 20 visuallyAdd and subtract within 20 word problemsAddition and subtraction word problems: superheroesAdding within 20 using place value blocksAddition and subtraction word problems: gorillasAdding within 20 using ten frames

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