①

1

2

x-

1

4

=

2

5

1

2

x+

1

4

-

1

4

=

2

5

+

1

4

1

2

x=0.65

1

2

x×2=0.65×2

x=1.3

②x+

7

8

x=

3

4

15

8

x=

3

4

15

8

×

8

15

x=

3

4

×

8

15

x=

2

5

③

2

3

x÷

1

4

=12

2

3

x×4=12

8

3

x=12

8

3

x×

3

8

=12×

3

8

x=4.5