Question 895440
Square of side s, and rectangle of sides x and y.


{{{s^2=3xy}}};
{{{x=40}}}, assigning x as length of the rectangle;
{{{y=(3/2)s}}}.


Simplify using substitution for x=40.
{{{s^2=3*40y}}} and {{{y=(3/2)s}}}.
{{{s^2=120y}}}
More than one set of steps, but solving for s in the linear equation seems like a good way.
{{{s=(2/3)y}}}
And substitute into the s^2 equation:
{{{((2/3)y)^2=120y}}}
{{{(4/9)y^2=120y}}}
{{{y^2=(9/4)120y}}}
{{{y^2=9*30y}}}
{{{y^2=270y}}}
{{{y^2-270y=0}}}
{{{y(y-270)=0}}}
{{{y<>0}}} so the solution for y is {{{highlight(y=270)}}}.


Going back a few steps, notice s=(2/3)y
{{{s=(2/3)270}}}
{{{highlight(s=180)}}}------side length of the square.