\[\boxed{\mathbf{1.}}\]
\[1)\ 36,6 + 2,3 = 38,9{^\circ}\]
\[2)\ 38,9 - 1,8 = 37,1{^\circ}\]
\[\boxed{\mathbf{2.}}\]
\[1)\frac{1}{3}x = 5\]
\[x = 5 \cdot 3\]
\[x = 15.\]
\[2)\ 3x = 5\]
\[x = 5\ :3\]
\[x = \frac{5}{3} = 1\frac{2}{3}.\]
\[3)\ 3x = \frac{1}{5}\]
\[x = \frac{1}{5 \cdot 3}\]
\[x = \frac{1}{15}.\]
\[4)\frac{1}{3}x = \frac{1}{5}\]
\[x = \frac{1 \cdot 3}{5 \cdot 1}\]
\[x = \frac{3}{5}.\]
\[\boxed{\mathbf{3.}}\]
\[\boxed{\mathbf{4.}}\]
\[На\ 11\ этаже\ или\ на\ 3\ этаже.\]
\[Задача\ имеет\ два\ решения.\]