9.9×3.5=(10-0.1)×3.5=10×3.5-0.1×3.5=35-0.35=34.65
=（10-0.1）×3.5=10×3.5-0.1×3.5=35-0.35=34.65
9.9×3.5=10×3.5-0.1×3.5=35-0.35=34.65
