18．计算下面各题，能简算的要简算，并写出简算过程．
| 179+54+321 | 115×23-23×15 | 15.25-3.1+0.75-4.9 |
| 6×8×1.25 | 124×5+169÷13 | （420+60）÷（375-345） |
17．直接写出得数
0 157792 157800 157806 157810 157816 157818 157822 157828 157830 157836 157842 157846 157848 157852 157858 157860 157866 157870 157872 157876 157878 157882 157884 157886 157887 157888 157890 157891 157892 157894 157896 157900 157902 157906 157908 157912 157918 157920 157926 157930 157932 157936 157942 157948 157950 157956 157960 157962 157968 157972 157978 157986 199269
| 1050+150= | 76-38= | 102×3= | 2.65+0.73= |
| 240÷16= | 25×8= | 2.12-0.9= | 1+0.2= |
| 0.54-0.45= | 3.25+1= | 1.4-0.5= | 1-0.25= |