\(\frac{21}{11}\cdot\frac{68}{63}\cdot\frac{22}{17}\)
\(=1\cdot\frac{4}{3}\cdot2\)
\(=\frac{8}{3}\)
\(\left(\frac{27}{25}-\frac{4}{9}\right)-\left(\frac{2}{25}+\frac{5}{9}\right)\)
\(=\frac{27}{25}-\frac{4}{9}-\frac{2}{25}-\frac{5}{9}\)
\(=\left(\frac{27}{25}-\frac{2}{25}\right)-\left(\frac{4}{9}+\frac{5}{9}\right)\)
\(=1-1\)
\(=0\)