\[\boxed{\mathbf{1}.}\]
\[1)\ 102;\]
\[2)\ 306;\]
\[3)\ 315.\ \]
\[\boxed{\mathbf{2}.}\]
\[(21 - 1)\ :4 = 5\ \left( \frac{км}{ч} \right) -\]
\[скорость\ туриста.\]
\[Ответ:5\ \frac{км}{ч}.\]
\[\boxed{\mathbf{3}.}\]
\[40 < x < 50\]
\[x = 41;43;47.\]
\[\boxed{\mathbf{4}.}\]
\[1)\ нет:\]
\[120 = 2 \cdot 2 \cdot 2 \cdot 3 \cdot 5.\]
\[2)\ нет:\]
\[567 = 3 \cdot 3 \cdot 3 \cdot 3 \cdot 7.\]
\[3)\ нет:\]
\[180 = 2 \cdot 2 \cdot 3 \cdot 3 \cdot 5.\]