（1）18x+7×0.9=8.64

              18x+6.3=8.64

                     18x=2.34

                        x=0.13（2）（5+x）×1.5=150

                        5+x=100

                            x=95

（3）24x-6.5x=35.525

              17.5x=35.525

                    x=2.03（4）8x-7.5x=17.4

              0.5x=17.4

                  x=34.8