Tìm x :a) x – 123 = 345 b) x + 254 = 665

* Hướng dẫn giải

a) x – 123 = 345                                                         b) x + 254 = 665

         x      = 345 + 123                                                    x          = 665 – 254

         x      =  468                                                                x       = 211