（1）解： 35 -2.5x＝5

                      2.5x=30

                          x=12（2）解：6×2.5+8x=23

                            8x=23-15

                              x=1

（3）解：1.2x+1.3x-8=4.6

                           2.5x=12.6

                               x=5.04（4）解：（2.5 +x）×1.4= 11.9

                                  1.4x=11.9-3.5

                                      x=6