a)
[tex]\left \{ {{3x-4y=-2} \atop {6x+2y=6}} \right. \\\left \{ {{3x-4y=-2} \atop {2y=6-6x}} \right. \\\left \{ {{3x-4y=-2} \atop {y=3-3x}} \right. \\3x-4(3-3x)=-2\\3x-12+12x=-2\\15x=10\\x=\frac{2}{3}\\y=3-3*\frac{2}{3}\\y=3-2\\y=1\\\left \{ {{x=\frac{2}{3} \atop {y=1\\}} \right.[/tex]
b)
[tex]\left \{ {{\frac{5x+2y}{3} -\frac{2x-1}{2}=1 } \atop {\frac{3-x}{2}-2y=3 }} \right. \\\left \{ {{2(5x+2y)-3(2x-1)=6 \atop {3-x-4y=6}} \right. \\\left \{ {{10x+4y-6x+3=6} \atop {-x-4y=3}} \right. \\\left \{ {{4x+4y=3} \atop {-x-4y=3}} \right. \\\left \{ {{4x+4y=3} \atop {x=-4y-3}} \right. \\4(-4y-3)+4y=3\\-16y-12+4y=3\\-12y=15\\y=-0,8\\x=-4*(-0,8)-3\\x=3,2-3\\x=0,2\\\left \{ {{x=0,2} \atop {y=-0,8\\}} \right.[/tex]
c)
[tex]\left \{ {{0,5x-3y=2} \atop {-4x-y=9}} \right. \\\left \{ {{x-6y=4} \atop {-4x-y=9}} \right. \\\left \{ {{x=6y+4 \atop {-4x-y=9}} \right. \\-4(6y+4)-y=9\\-24y-16-y=9\\-25y=25\\y=-1\\x=6*(-1)+4\\x=-6+4\\x=-2\\\left \{ {x=-2} \atop {y=-1}} \right.[/tex]
