Ответ:\(200+570=770\), \(770-300=470\), \(470:10=47\), \(47+10=57\).\(200+480=680\), \(680-300=380\), \(380-30=350\), \(350-200=150\).\(200+80=280\), \(280-280=0\), \(0:5=0\), \(0:4=0\).Ответ: а) 57; б) 150; в) 0.