2√7-  \(\frac{14}{√7} + \frac{7}{√21}\)

L.C.M is √21

\(\frac{√21 * 2√7 - √3 *14  + 7}{√21}\)

=\(\frac{2 * 7√3 - 14√3 + 7}{√21}\)

= \(\frac{14√3 - 14√3 + 7}{√21}\)

=\(\frac{7}{√21}\)

or 

\(\frac{7 \times √21}{√21 \times √21}\) 

= \(\frac{7 \times √21}{21}\) or \(\frac{√21}{3}\)