2.9x9.9+0.29=2.9x9.9+2.9x0.1=2.9x(9.9x0.1)(乘法分配律)=2.9x10=29
3.9×9点90+0点29的=3.9*10-0.1*3.9+0.29=38.9多看概念基础才好
2.9x9.9+0.29=2.9x9.9+2.9x0.1=2.9x(9.9+0.1)=2.9x10=29希望能帮到你!