Question 314502
{{{P1=2*(L+W)=62}}}
1.{{{L+W=31}}}
.
.
.
{{{P2=2*(L+21+2W)=120}}}
{{{L+2W+21=60}}}
2.{{{L+2W=39}}}
Subtract eq. 1 from eq. 2,
{{{L+2W-L-W=39-31}}}
{{{highlight_green( W=8)}}}
Then from eq. 1,
{{{L+8=31}}}
{{{highlight_green( L=23)}}}