我会用巧妙方法来计算．12.9×97+12.9×4-12.957.8-14.25-15.7558×0.25×45×47.5×45+1.5×80%+0.8．

Question

我会用巧妙方法来计算．
12.9×97+12.9×4-12.9            
57.8-14.25-15.75
(5)/(8)×0.25×(4)/(5)×4                  
7.5×(4)/(5)+1.5×80%+0.8．

Answer 1

（1）12.9×97+12.9×4-12.9=12.9×（97+4-1）=12.9×100=1290；（2）57.8-14.25-15.75=57.8-（14.25+15.75）=57.8-30=27.8；（3）58×0.25×45×4=（58×45）×（0.25×4）=12×1=12；（4）7.5×45+1.5×80%+0.8=7....