447 + 368 ------ 815
456 + 378 ------ 834
532 - 278 ------ 254
821 - 456 ------ 365
Ответ: \(447 + 368 = 815\), \(456 + 378 = 834\), \(532 - 278 = 254\), \(821 - 456 = 365\)