Question 771174
Let the length of rectangle to be a while the width to be b.
{{{2a+2b=6x+10}}}
{{{2a/2+2b/2=6x/2+10/2}}}
{{{a+b=3x+5}}}
The length, {{{a=3x+5-b}}}.
The width, {{{b=3x+5-a}}}