Question 897362
{{{A=L*W=70}}}
{{{(W+3)W=70}}}
{{{W^2+3W=70}}}
{{{W^2+3W-70=0}}}


{{{(W+10)(W-7)=0}}}
Only the positive solution makes sense here.
{{{W-7=0}}}
{{{W=7}}}{{{in}}}
Then,
{{{L=7+3}}}
{{{L=10}}}{{{in}}}