答：
-1/42÷(1/6-2/7+2/3-3/14)
＝－1/[42×(1/6-2/7+2/3-3/14)]
＝－1/(42/6-42*2/7+42*2/3-42*3/14)
＝－1/(7-12+28-9)
＝－1/14
回答完毕.