Ответ:\(6a+2a-3a=5a\).\(12b-7b+4=5b+4\).\(8y-5+y+2=9y-3\).\(-4x+9x-2x=3x\).\(7m-3+2-5m=2m-1\).\(-6c+4c+8-1=-2c+7\).