\(\left(\frac{1}{15}+\frac{1}{35}+\frac{1}{63}\right)\times x=1\)
\(\Rightarrow\left(\frac{21}{315}+\frac{9}{315}+\frac{5}{315}\right)\times x=1\)
\(\Rightarrow\frac{35}{315}\times x=1\)
\(\Rightarrow x=1\div\frac{35}{315}\)
\(\Rightarrow x=\frac{315}{35}\)