21 加法 7 等于多少？
21 + 7 = 28
21加法7 等于 28
竖式演算
验算
- 用减法验算：28 − 7 = 21
- 用减法验算：28 − 21 = 7
相关题目
21 + 6 = 27
21 + 8 = 29
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21 + 9 = 30
21 + 4 = 25
21 + 10 = 31
21 + 11 = 32
21 + 3 = 24
20 + 7 = 27
22 + 7 = 29
19 + 7 = 26
23 + 7 = 30
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2 + 26 = 28
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