Question 901917
Do you mean 
{{{(4+y)(4+x)=56}}}
{{{yx=24}}}?
If so, there's no solution.
{{{graph(300,300,-15,15,-100,100,24/x,56/(4+x)-4)}}}
.
.
.
Did you mean 
{{{4+4y+x=56}}}
{{{xy=24}}}
.
.
.
{{{y=24/x}}}
Substituting,
{{{4+4(24/x)+x=56}}}
{{{96/x+x=52}}}
{{{96+x^2=52x}}}
{{{x^2-52x+96=0}}}
{{{x^2-52x+676+96=676}}}
{{{(x-26)^2=580}}}
{{{x-26=0 +- sqrt(580)}}}
{{{x=26 +-2*sqrt(145)}}}
Then,
{{{y=24/(26 +- 2 sqrt(145))}}}
{{{y=12/(13 +- sqrt(145))}}}
.
.
{{{graph(300,300,-10,90,-10,40,24/x,(52-x)/4)}}}