Ответ:\(16 + 4x = 128\);\(4x = 128 - 16\);\(4x = 112\);\(x = 28\).\(400 - 6x = 276 + 2x\);\(400 - 276 = 2x + 6x\);\(124 = 8x\);\(x = 15.5\).Ответ: а) \(x = 28\); б) \(x = 15,5\).