20．解方程．
| 78.4-3x=40 | 2.5x+12=30.6 | x-0.75x=120 |
| 2.2x-x=0.3 | （x-3）×2=26.4 | （x+1）×1.2=6.72 |
12．假分数带分数互化．
0 157876 157884 157890 157894 157900 157902 157906 157912 157914 157920 157926 157930 157932 157936 157942 157944 157950 157954 157956 157960 157962 157966 157968 157970 157971 157972 157974 157975 157976 157978 157980 157984 157986 157990 157992 157996 158002 158004 158010 158014 158016 158020 158026 158032 158034 158040 158044 158046 158052 158056 158062 158070 199269
| $\frac{41}{15}$= | $\frac{38}{20}$= | $\frac{65}{3}$= | $\frac{27}{13}$= | 8$\frac{3}{4}$= | 9$\frac{5}{7}$= | 4$\frac{1}{2}$= | 3$\frac{3}{5}$= |