4b+(r-b)*2=4b+2r+2b=6b+2r;
(4+12)*a+7*c=4a+12a+7c=16a+7c;
(6+5+8)*c-9*a=6c+5c+8c-9a=19c-9a;
17*b-4*b+8*c=17b-4b+8c=13b+8c;
56*d+(6+7)*d=56d+6d+7c=69d;
5*(a+b+c)+2*b=5a+5b+5c+2b=5a+7b+5c;
(d+c)*5+4*d=5d+5c+4d=9d+5c;
(d+c)*4-2*d=4d+4c-2d=2d+4c;
62*c-34*c+6*c=62c-34c+6c=34c;