Let missing side be x
Using basic proportionality theorem
[tex]\\ \sf\longmapsto \dfrac{45}{35}=\dfrac{x}{56}[/tex]
[tex]\\ \sf\longmapsto \dfrac{9}{7}=\dfrac{x}{56}[/tex]
[tex]\\ \sf\longmapsto 7x=9(56)[/tex]
[tex]\\ \sf\longmapsto x=\dfrac{9(56)}{7}[/tex]
[tex]\\ \sf\longmapsto x=72[/tex]
