Verified answer

Ответ:

A)

Объяснение:

b=a-1/2

a-1/2=2c+1/2

2c=a-1/2-1/2

2c=a-1

c=(a-1)/2

c=3d+1/2

(a-1)/2=3d+1/2

a/2-1/2-1/2=3d

3d=a/2-1

d=(a-2)/(2*3

d=(a-2)/6