> restart;

> with(plots):

Warning, the name changecoords has been redefined

> Rest:=[x<=7,x+3*y>=15,3*x+y>=9, x-5*y>=-30];

> Regiao_factivel:=inequal(Rest, x=0..15,y=0..10, optionsfeasible=(color=blue),optionsexcluded=(color=white)):

> display([Regiao_factivel]);

> curvas:=contourplot(5*x+6*y,x=0..10,y=0..10,contours=[50,60,70],linestyle=4,numpoints=1000,color=gray):

> display([Regiao_factivel,curvas]);

> sol:=solve({x=7,x-5*y=-30},{x,y});

> assign(sol);

> z:=5*x+6*y;

>