Find the missing number.
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You can use the opposite calculation to solve or check calculations.
+ 9 = 20
- Read the question and read it again. What do you have to do?
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- What is the opposite calculation?
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20 – 9 =
- Use what you know to find the missing number.
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20 – 9 = 11
- What is your answer?
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11
- Check your answer.