(-2/7+1/6-3/14+2/3)/(-1/42)
=(2/7-1/6+3/14-2/3)/(1/42)
=42*(2/7-1/6+3/14-2/3)
=42*2/7-42*1/6+42*3/14-42*2/3
=12-7+9-28
=-14