解：80.45-(25.6-14.9) =80.45-25.6+14.9 =80-25+14+(0.45+0.9-0.6) =69+(0.45+0.3) =69+0.75 =69.75
见图
可以去掉括号计算原式＝80.45-25.6+14.9＝54.85+14.9＝69.75
