\(=\frac{\frac{1}{3}.\left(\frac{1}{2}-\frac{1}{13}+\frac{1}{17}\right)}{\frac{1}{4}.\left(\frac{1}{2}-\frac{1}{13}+\frac{1}{17}\right)}=\frac{4}{3}\)
\(\frac{\frac{1}{6}-\frac{1}{39}+\frac{1}{51}}{\frac{1}{8}-\frac{1}{52}+\frac{1}{68}}=\frac{\frac{1}{3}.\left(\frac{1}{2}-\frac{1}{13}+\frac{1}{17}\right)}{\frac{1}{4}.\left(\frac{1}{2}-\frac{1}{13}+\frac{1}{17}\right)}=\frac{4}{3}\)
\(\frac{\frac{1}{3}x\frac{1}{2}-\frac{1}{3}x\frac{1}{13}+\frac{1}{3}x\frac{1}{17}}{\frac{1}{4}x\frac{1}{2}-\frac{1}{4}x\frac{1}{13}+\frac{1}{4}x\frac{1}{17}}\)
\(\frac{\frac{1}{3}x\left(\frac{1}{2}-\frac{1}{13}+\frac{1}{17}\right)}{\frac{1}{4}x\left(\frac{1}{2}-\frac{1}{13}+\frac{1}{17}\right)}\)
\(=\frac{\frac{1}{3}}{\frac{1}{4}}=\frac{4}{3}\)