Tính (theo mẫu). Mẫu: 768 – 124 + 345 = 644 + 345                

876 – 529 + 201 = 347 + 201   

                       = 548                                                                 

168 – 129 + 510 = 39 + 510

                        = 549

187 + 107 – 205 = 294 – 205

                       = 89                                                               

564 – 325 + 251 = 239 + 251

                       = 490