（1）2x+4.5×4=39

                2x+18=39

                      2x=21

                        x=10.5（2）1.5x-1.2x=2.4×3

                 0.3x=7.2

                      x=24（3）3.6×（x-2）=7.2

                        x-2=7.2÷3.6

                           x= 4