2- 3/8÷7/17-1/7
=2-3/8×17/7-1/7
=2-51/56-1/7
=53/565/12÷8+1/8×12/75/12÷8+1/8×7/12
=5/12×1/8+1/8×7/12
=1/8×(5/12+7/12)
=1/8×1
=1/8

采纳吧 O(∩_∩)O谢谢