\frac{3,5*(-1\frac{3}{7})-(\frac{2}{3})^2}{(1-\sqrt{1\frac{7}{9}})*7}=\frac{-\frac{35}{10}*(-\frac{10}{7})-\frac{4}{9}}{(1-\sqrt{\frac{16}{9}})*7}=
=\frac{-5-\frac{4}{9}}{(1-\frac{4}{3})*7}=\frac{-5\frac{4}{9}}{(-\frac{1}{3})*7}=-\frac{49}{9}*(-\fra{3}{7})=\frac{7}{3}=2\frac{1}{3}