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19+3\frac{1}{5}=19\frac{1}{5}
2)
23-3\frac{4}{5}=22\frac{5}{5}-3\frac{4}{5}=19\frac{1}{5}
albo
23-3\frac{4}{5}=\frac{115}{5}-\frac{19}{5}=\frac{96}{5}=19\frac{1}{5}
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\not6^2 \cdot \frac{1}{\not3^1}=2\cdot 1=2
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12:\frac{4}{9}=\not12^3\cdot \frac{9}{\not4^1}=3\cdot 9=27