（1）12x-3×5=105

             12x-15=105

                  12x=90

                      x=7.5（2）90×（x÷2）=36

                       x÷2=0.4

                            x=0.8

（3）9.25-4x=1.5

                4x=7.75

                  x=1.9375（4）4x-0.5x=0.35×2

             3.5x=0.7

                  x=0.2