Ответ:
\[\frac{1}{7}+\frac{6}{49}=\frac{7}{49}+\frac{6}{49}=\frac{13}{49}.\]
\[\frac{7}{39}\cdot\frac{13}{49}=\frac{1}{21}.\]
Ответ: \(\frac{1}{21}\).
\[\frac{1}{7}+\frac{6}{49}=\frac{7}{49}+\frac{6}{49}=\frac{13}{49}.\]
\[\frac{7}{39}\cdot\frac{13}{49}=\frac{1}{21}.\]
Ответ: \(\frac{1}{21}\).