A:H2
B:NaCl
C:NaOH
D:H2S
70+80____70+60 5800–800____6000–3000 130+70____200+20
700–90____700–80 1200–200____1000+200 500–50____400+50
100+50____200–60 100–60____100-70
看一本140页的故事书,已经看了全书总页数的 47 ,还有多少页没有看?