Question 1006268
the perimeter of rectangle is

{{{P=2L+2W}}}

so,

{{{2L+2W=56cm}}}


if the length of the rectangle is {{{4}}} less than {{{3}}} times the width, then we have

{{{L=3W-4}}}

{{{2(3w-4cm)+2(w)=56cm}}}


{{{6w-8cm+2w=56cm}}}

{{{8w=56cm+8cm}}}

{{{8w=64cm}}}

{{{w=64cm/8}}}

{{{w=8cm}}}

then the length is

{{{L=3*8cm-4cm}}}

{{{L=24cm-4cm}}}

{{{L=20cm }}}