$A={{\left( 2-1\frac{2}{5} \right)}^{2}}+\left| 1-\frac{12}{5} \right|-{{\left( \frac{-2}{5} \right)}^{2}}$

$\,\,={{\left( 2\frac{5}{5}-1\frac{2}{5} \right)}^{2}}+\left| \frac{5}{5}-\frac{12}{5} \right|-{{\left( \frac{-2}{5} \right)}^{2}}$

$\,\,={{\left( \frac{3}{5} \right)}^{2}}+\left| \frac{-7}{5} \right|-{{\left( \frac{-2}{5} \right)}^{2}}$

$\,\,={{\left( \frac{3}{5} \right)}^{2}}+\frac{7}{5}-{{\left( \frac{-2}{5} \right)}^{2}}$

$\,\,={{\left( \frac{3}{5} \right)}^{2}}+\frac{7.5}{{{5}^{2}}}-{{\left( \frac{-2}{5} \right)}^{2}}=\frac{8}{5}$

$B=\frac{1}{2}-\frac{3}{7}:\left( -2\frac{1}{7} \right)+\left| \frac{1}{5}-\frac{1}{2} \right|-\frac{2}{5}$

 $\,=\frac{1}{2}-\frac{3}{7}:\left( -\frac{15}{7} \right)+\left| \frac{2}{10}-\frac{5}{10} \right|-\frac{2}{5}$

 $\,=\frac{1}{2}+\frac{1}{5}+\frac{3}{10}-\frac{2}{5}$

$\,=\frac{3}{5}$

VẬY tỉ số:

$\frac{A}{B}=\frac{8}{5}:\frac{3}{5}=\frac{8}{3}$