5.8 + 2.9 x 8 =2.9 x 2 + 2.9 x 8 =2.9 x （2 + 8）=2.9 x 10 =29
2.9×64+5.8×18＝2.9×64+2.9×2×18＝2.9×（64+36）＝290
