Question 1115410

given: 
A rectangle has a perimeter of {{{56cm}}}. 

=> {{{P=2(L+W)}}}

=> {{{2(L+W)=56cm}}}

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

=> {{{L+W=28cm}}}

=> {{{L=28cm-W}}}....eq.1

if the length is {{{4cm}}} less than {{{3}}} times width, we have:

{{{L=3W-4cm}}}...eq.2 ...substitute in eq.1


{{{3W-4cm=28cm-W}}}

{{{3W+W=28cm+4cm}}}

{{{4W=32cm}}}

{{{W=32cm/4}}}

{{{highlight(W=8cm)}}}

now find the length:

{{{L=28cm-W}}}....eq.1

{{{L=28cm-8cm}}}

{{{highlight(L=20cm)}}}

so, dimensions are:{{{highlight(L=20cm)}}},{{{highlight(W=8cm)}}}