$\text{a)}\frac{4}{3},\frac{6}{1},\frac{5}{3}$      

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$\text{b)}\frac{1}{2},\frac{1}{4},\frac{1}{12}$  

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$\text{c)}$  

$\frac{1}{1\frac{1}{2}}=\frac{1}{\frac{3}{2}}=\frac{2}{3}$  

$\frac{1}{2\frac{2}{3}}=\frac{1}{\frac{8}{3}}=\frac{3}{8}$  

$\frac{1}{3\frac{5}{6}}=\frac{1}{\frac{23}{6}}=\frac{6}{23}$