\[\boxed{\mathbf{2.}\mathbf{102}}\]
Пояснение.
Решение.
\[\textbf{а)}\ \frac{7}{15}\ и\ \frac{5}{12}\]
\[15 = 3 \cdot 5;\ \ 12 = 2 \cdot 2 \cdot 3\]
\[НОК(15,\ 12) = 3 \cdot 5 \cdot 2 \cdot 2 = 60.\]
\[\textbf{б)}\ \frac{13}{20}\ и\ \frac{17}{25}\]
\[20 = 2 \cdot 2 \cdot 5;\ \ 25 = 5 \cdot 5\]
\[НОК(25,\ 20) = 5 \cdot 5 \cdot 2 \cdot 2 =\]
\[= 100.\]