Let it be x
[tex]\\ \sf\longmapsto \dfrac{150}{x}=\dfrac{150+150}{280}[/tex]
[tex]\\ \sf\longmapsto \dfrac{150}{x}=\dfrac{300}{280}[/tex]
[tex]\\ \sf\longmapsto \dfrac{1}{x}=\dfrac{2}{280}[/tex]
[tex]\\ \sf\longmapsto \dfrac{1}{x}=\dfrac{1}{140}[/tex]
[tex]\\ \sf\longmapsto x=140ft[/tex]
