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Education Concept Tracker

A prerequisite knowledge graph of 1590 learning concepts across 8subjects. Track what you've mastered and see exactly what you're ready to learn next — the topics whose prerequisites you've already met. Built on the Marble Open Skill Taxonomy.

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Unknown in Addition & Subtraction

Mathematics · Addition & Subtraction · procedural

Determine the unknown whole number in an addition or subtraction equation relating three whole numbers

What mastery looks like

  • Solve 8 + ? = 11 and write 3
  • Solve 5 = □ − 3 and write 8
  • Solve 6 + 6 = □ and write 12

Check your understanding

If Unknown in Addition & Subtraction sees '? + 6 = 14' or '9 − ? = 4' written on paper, can they figure out what number goes in the gap?