c c
-b - - + 3*b - --
7 14
-b - c/7 + 3*b - c/14
/ 3*c\ 1*|b - ---| \ 28/
1*(b - 3*c/28)
3*c
2*b - ---
14
-21*c + 196*b
-------------
98
(-21*c + 196*b)/98
-3*c + 28*b
-----------
14
(-3*c + 28*b)/14