\[\boxed{\text{1130.\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]
\[f(x) = \sqrt{x}.\]
\[\textbf{а)}\ f(x) > 10:\]
\[\sqrt{x} > 10\]
\[x > 100.\]
\[\textbf{б)}\ 3 < f(x) < 5:\]
\[3 < \sqrt{x} < 5\]
\[9 < x < 25.\]