2.9x6.7++2.9+2.9x2.3＝2.9x（6.7+1+2.3）＝2.9x10＝29运用乘法分配律。
2.9✘(6.7+2.3+1)=2.9✘10=29
2.9*6.7+2.9+2.9*2.3=2.9*（6.7+1+2.3）=2.9*10=29
