[tex]\bf 6.\ \ \it [51,73]=51;\ \ [-8,12]=-9;\ \ \Big[\dfrac{8}{5}\Big]=[1,6]=1\\ \\ \\ \Big[-\dfrac{11}{5}\Big]=[-2,2]=-3;\ \ [21]=21;\ \ [-0,32]=-1[/tex]
[tex]\bf 7.\ \ \it \dfrac{x}{1+\dfrac{1}{3}}=\dfrac{5}{0,(6)} \Rightarrow \dfrac{x}{\dfrac{4}{3}}=\dfrac{5}{\dfrac{6}{9}} \Rightarrow x=\dfrac{5\cdot\dfrac{4}{3}}{\dfrac{6}{9}}=\dfrac{20}{3}\cdot\dfrac{9}{6}=\dfrac{180}{18}=10[/tex]