2(b+c)-(b-c)
2b+2c-b+c
2*-2 1/3+2*1/27=-14/3+2/27=-126/27+2/27=-124/27
-124/27-(-7/3)=-124/27+63/27=-61/27
-61/27+1/27=-60/27=-2 6/27= -2 2/9
2(b+c)-(b-c)
2b+2c-b+c
2*-2 1/3+2*1/27=-14/3+2/27=-126/27+2/27=-124/27
-124/27-(-7/3)=-124/27+63/27=-61/27
-61/27+1/27=-60/27=-2 6/27= -2 2/9