0,2\sqrt{50}+0,8\sqrt{72}-0,3\sqrt{32}=
=0,2\sqrt{25*2}+0,8\sqrt{36*2}-0,3\sqrt{16*2}=
=0,2*5\sqrt2+0,8*6\sqrt2-0,3*4\sqrt2=\sqrt2+4,8\sqrt2-1,2\sqrt2=4,6\sqrt2
,
3\sqrt{20}-\frac{1}{3}\sqrt{45}-5\sqrt{180}=
=3\sqrt{4*5}-\frac{1}{3}\sqrt{9*5}-5\sqrt{36*5}=
=3*2\sqrt5-\frac{1}{3}*3\sqrt5-5*6\sqrt5=
=6\sqrt5-\sqrt5-30\sqrt5=-25\sqrt5