9/10-(4/5+1/4)÷3/7=9/10-(16/20+5/20)÷3/7=9/10-21/20*7/3=9/10-49/20=18/20-49/20=-31/20
(4/5+1/4)÷7/3+7/10=(16/20+5/20)÷7/3+7/10=21/20÷7/3+7/10=49/20+14/20=63/20