$\dfrac{3}{4}\sqrt{\dfrac{4}{9}}-\dfrac{2}{5}\sqrt{\dfrac{5}{2}}-2\sqrt{0,36}=\dfrac{3}{4}.\dfrac{2}{3}-\dfrac{2}{5}.\dfrac{\sqrt{10}}{2}-2\sqrt{\dfrac{9}{25}}
\\=\dfrac{1}{2}-\dfrac{\sqrt{10}}{5}-\dfrac{6}{5}=\dfrac{5-2\sqrt{10}-12}{10}=-\dfrac{7+2\sqrt{10}}{10}$