[tex]\displaystyle\bf\\\left \{ {{3+3,2x\geq 7-1,8x} \atop {5+6x\geq 4,5+4x}} \right. \\\\\\\left \{ {{3,2x+1,8x\geq 7-3} \atop {6x-4x\geq 4,5-5}} \right. \\\\\\\left \{ {{5x\geq 4} \atop {2x\geq -0,5}} \right. \\\\\\\left \{ {{x\geq 0,8} \atop {x\geq -0,25}} \right. \ \ \Rightarrow \ \ \ x\geq 0,8\\\\\\Otvet: \ x\in\Big[0,8 \ ; \ +\infty\Big)[/tex]