Question 895099
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The "length" seems 3y+4; and the other dimension, the width, is then y+3.


For perimeter of 70,
{{{2(3y+4)+2(y+3)=70}}}
{{{3y+4+y+3=35}}}
{{{4y+7=35}}}
{{{4y=28}}}
{{{highlight(y=7)}}}