7.2×0.68+0.72×3.3-0.072=7.2×0.68+7.2×0.33-7.2×0.01=7.2×(0.68+0.33-0.01)=7.2×1=7.2
7.2×0.68+0.72×3.3-0.072=7.2×（0.68+0.33-0.01）=7.2×1=7.2
