210

$\left|\overline{a}\right|=\sqrt{\frac{1}{9}+\frac{1}{16}}=\frac{5}{12}\left(tai\ -\frac{5}{12}\right)$
$\overline{a}^0=\frac{\overline{a}}{\left|\overline{a}\right|}=\frac{\frac{1}{3}\overline{\text{i}}-\frac{1}{4}\overline{\text{j}}}{\frac{5}{12}}=\frac{4}{5}\overline{\text{i}}-\frac{3}{5}\overline{\text{j}}$

$\overline{v}=-6\overline{a}^0=-6\left(\frac{4}{5}\overline{\text{i}}-\frac{3}{5}\overline{\text{j}}\right)=-\frac{24}{5}+\frac{18}{5}=-4\ \frac{4}{5}\overline{\text{i}}+3\ \frac{3}{5}\overline{\text{j}}$