[tex]\left \{ {{\frac37x+\frac47y=84 /*7} \atop {\frac47x+\frac37y=96 /*7}} \right. \\\left \{ {{3x+4y=588 /*4} \atop {4x+3y=672 /*(-3)}} \right. \\+\left \{ {{12x+16y=2352} \atop {-12x-9y=-2016}} \right. \\16y-9y=2352-2016\\7y=336 /:7\\y=48\\\\\frac37x+\frac47*48=84\\\frac37x+\frac{192}7=\frac{588}7 /*7\\3x+192=588 /-192\\3x=396/:3\\x=132[/tex]
Odp. Kawy kosztuja 132zl/kg oraz 48zl/kg
