7.5x9.9=7.5x(10-0.1)=7.5x10-7.5x0.1=75-0.75=74.25 如果帮到你，请记得采纳，O(∩_∩)O谢谢
=7.5×(10-0.1)=7.5×10-7.5×0.1=75-0.75=74.25
=7.5×（10-0.1）=7.5×10-7.5×0.1=75-0.75=74.25
