\[\boxed{\mathbf{900\ (900).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ 3\sqrt{10} = \sqrt{90}\]
\[2)\ 2\sqrt{13} = \sqrt{52}\]
\[3)\ 0,3\sqrt{3} = \sqrt{0,27}\]
\[4)\frac{1}{5}\sqrt{175} = \sqrt{7}\]
\[5)\frac{2}{7}\sqrt{98} = \sqrt{\frac{4 \cdot 98}{49}} = \sqrt{8}\]
\[6) - 5\sqrt{7} = - \sqrt{175}\]
\[7) - 0,5\sqrt{30} = - \sqrt{0,25 \cdot 30} =\]
\[= - \sqrt{7,5}\]
\[8)\ 4\sqrt{a} = \sqrt{16a}\]