`5/7+x/35=4/5`
`=>x/35=4/5-5/7`
`=>x/35=28/35-25/35`
`=>x/35=3/35`
`=>x=3`
\(a.\dfrac{5}{7}+\dfrac{x}{35}=\dfrac{4}{5}\\ \dfrac{x}{35}=\dfrac{4}{5}-\dfrac{5}{7}\\ \dfrac{x}{35}=\dfrac{3}{35}\\x=\dfrac{35\times3}{35} \\ x=3.\)
\(\dfrac{5}{7}+\dfrac{x}{35}=\dfrac{4}{5}\)
⇒\(\dfrac{x}{35}=\dfrac{4}{5}-\dfrac{5}{7}\)
⇒\(\dfrac{x}{35}=\dfrac{28}{35}-\dfrac{25}{35}\)
⇒\(\dfrac{x}{35}=\dfrac{3}{35}\)
⇒x=3