[tex]l-length\\w-width\\\\\text{The formula of an area of a rectangle:}\ V=lw\\\\\text{We have the area}\ 540\ m^2\to lw=540\\\\\text{New rectangle}\\\\l-5-length\\w+5-width\\\\\text{We have the area}\ 540\ m^2+35\ m^2=575\ m^2\to (l-5)(w+5)=575\\\\\text{Therefore we have the system of equation:}\\\\\left\{\begin{array}{ccc}lw=540&\to w=\dfrac{540}{l}&(*)\\(l-5)(w+5)=575&&(**)\end{array}\right\\\\\text{Substitute}\ (*)\ \text{to}\ (**)[/tex]
[tex](l-5)\left(\dfrac{540}{l}+5\right)=575\qquad\text{use distributive property}\\\\(l)\left(\dfrac{540}{l}\right)+(5)(l)-(5)\left(\dfrac{540}{l}\right)-(5)(5)=575\\\\540+5l-\dfrac{2700}{l}-25=575\\\\515+5l-\dfrac{2700}{l}=575\qquad\text{subtract 575 from both sides}\\\\-60+5l-\dfrac{2700}{l}=0\qquad\text{multiply both sides by }\ l\neq0\\\\-60l+5l^2-2700=0\\\\5l^2-60l-2700=0\qquad\text{divide both sides by 5}\\\\l^2-12l-540=0\\\\l^2+30l-18l-540=0\\\\l(l+30)-18(l+30)=0\\\\(l+30)(l-18)=0\iff l+30=0\ \vee\ l-18=0\\\\l=-30<0\ \vee\ \boxed{l=18\ cm}[/tex]
[tex]\text{Substitute the value of}\ l\ \text{to}\ (*):\\\\w=\dfrac{540}{18}\\\\\boxed{w=30\ cm}[/tex]
[tex]Answer:\ \boxed{length=18\ cm,\ width=30\ cm}[/tex]
