$\frac{3}{4}=\frac{3\cdot 25}{4\cdot 25}=\frac{75}{100}=0,75$   

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$\frac{17}{20}=\frac{17\cdot 5}{20\cdot 5}=\frac{85}{100}=0,85$   

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$\frac{17}{25}=\frac{17\cdot 4}{25\cdot 4}=\frac{68}{100}=0,68$  

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$\frac{9}{50}=\frac{9\cdot 2}{50\cdot 2}=\frac{18}{100}=0,18$