Question 1044082
Graph the lines,
{{{7x+2y=3}}}
{{{7x+2y=-3}}}
{{{y-x=4}}}
{{{y-x=-4}}}
Look for the intersection points. 
The one with the maximum value will be the one that is most to the right and most above the x-axis.
In this case,
{{{x+y=-0.556+3.444=2.888}}}
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*[illustration gr6.JPG].