3√8-2√12+√20----------------------- =3√18-2√27+√45

[latex] frac{3 sqrt{8} -2 sqrt{12}+ sqrt{20} }{ 3sqrt{18}-2 sqrt{27}+ sqrt{45}} = frac{3 sqrt{4*2}-2 sqrt{4*3}+ sqrt{4*5}}{3 sqrt{9*2}-2 sqrt{9*3}+ sqrt{9*5}} = frac{6 sqrt{2}-4sqrt{3}+2sqrt{5}}{9sqrt{2}-6sqrt{3}+3sqrt{5}} = \ \ = frac{2(3 sqrt{2}-2sqrt{3}+sqrt{5})}{3(3sqrt{2}-2sqrt{3}+sqrt{5})} = frac{2}{3} [/latex]Ответ:   [latex] frac{2}{3} [/latex]