3. Represent the number $\frac{2}{7}$ as the sum of several different common fractions, the numerators of which are equal to one.

#
# Solution

We use the fact that

$$
\frac{1}{n}=\frac{1}{n+1}+\frac{1}{n(n+1)}
$$

Then

$$
\frac{2}{7}=\frac{1}{7}+\frac{1}{7}=\frac{1}{7}+\frac{1}{8}+\frac{1}{56}
$$

Other variations are also possible.

Any other correct representation was also accepted as an answer.