Question 1086843
First graph each inequality.
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*[illustration f1.JPG].
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*[illustration f2.JPG].
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*[illustration f3.JPG].
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Then overlay them to define the feasible region,
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*[illustration f4.JPG].
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Take out the inequality and just graph the boundary lines to make it more visually appealing and understandable.
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*[illustration f5.JPG].
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Find the vertices using the intersection of the boundary lines.
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Test the objective function at each of the vertices to find the maximum value,
I'll do one. 
You do the others the same way.
(4,12):{{{f=15(4)+25(12)=60+300=360}}}
Do the other two vertices the same way and see what the max value is and where it occurs.