[tex]w= \frac{3}{4} l[/tex]
[tex]w^{'}=w+3 [/tex]
[tex]l^{'}=l+3[/tex]
[tex]P=2( w^{'} + l^{'} )= 2((w+3)+(l+3))=2(w+l+6)=2w+2l+12[/tex]
[tex]=2*( \frac{3}{4} l)+2l+12 = \frac{3}{2} l+ \frac{4}{2} l+12=50 \\ \frac{7}{2}l =38 \\ l= \frac{38*2}{7} [/tex]
[tex]w= \frac{3}{4} l= \frac{3}{4} * \frac{38*2}{7} = \frac{19*3}{7} [/tex]