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The expression in the image is:

\[ 13 \div \left( \frac{1}{3} + \frac{2}{7} \right) \]

To solve it:

1. Find a common denominator for the fractions \(\frac{1}{3}\) and \(\frac{2}{7}\). The common denominator is 21.

\[ \frac{1}{3} = \frac{7}{21} \] \[ \frac{2}{7} = \frac{6}{21} \]

2. Add the fractions:

\[ \frac{7}{21} + \frac{6}{21} = \frac{13}{21} \]

3. Divide 13 by \(\frac{13}{21}\):

\[ 13 \div \frac{13}{21} = 13 \times \frac{21}{13} = 21 \]

So, the result is 21.