[tex]\displaystyle\bf\\a=1\frac{4}{5}:\frac{6}{5}-\left(1\frac{1}{4}\right)^{2}\times\frac{56}{75}\\\\\\a=\frac{1\times5+4}{5}:\frac{6}{5}-\left(\frac{1\times4+1}{4}\right)^{2}\times\frac{56}{75}\\\\\\a=\frac{9}{5}:\frac{6}{5}-\left(\frac{5}{4}\right)^{2}\times\frac{56}{75}\\\\\\a=\frac{9}{5}:\frac{6}{5}-\frac{25}{16}\times\frac{56}{75}\\\\\\a=\frac{9}{5}\times\frac{5}{6}-\frac{25}{16}\times\frac{56}{75}[/tex]
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[tex]\displaystyle\bf\\a=\frac{9\times5}{5\times6}-\frac{25\times56}{16\times75}\\\\\\a=\frac{9}{6}-\frac{56}{16\times3}\\\\\\a=\frac{9}{6}-\frac{7\times8}{2\times8\times3}\\\\\\a=\frac{9}{6}-\frac{7}{2\times3}\\\\\\a=\frac{9}{6}-\frac{7}{6}\\\\\\a=\frac{9-7}{6}\\\\\\a=\frac{~~2^{(2}}{6}\\\\\\\boxed{\bf~a=\frac{1}{3}}[/tex]
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[tex]\displaystyle\bf\\.....................\\\\a^3:\left(\frac{2}{3}\right)^2=\\\\\\=\left(\frac{1}{3}\right)^3:\left(\frac{2}{3}\right)^2=\\\\\\=\frac{1}{27}:\frac{4}{9}=\\\\\\=\frac{1}{27}\times\frac{9}{4}=\\\\\\=\frac{1\times9}{27\times4}=\\\\\\=\frac{1}{3\times4}=\boxed{\bf\frac{1}{12}}[/tex]
