笔算下面各题.358÷49470×56768÷49.
98+4×980+59×98.
用简便方法计算87×2.5+8.7×75 6.84×10.19.05﹣3.86﹣3.14.
667×668×669﹣666×668×670= .
12.5×3.2×25 56.8×0.17+1.7×4.02+0.03×179.76﹣2.084+0.24﹣0.916 9999×2222+3333×3334.
简算.87﹣2.123﹣0.877 26.3×78+2.63×220 25×5+74×5+5 444×25