2/5x2/10+9/10x0.4－2÷5x1/10 =2/5x2/10+9/10x2/5-2/5x1/10 =2/5x(2/10+9/10-1/10) =2/5x1 =2/5 补充：等于5分之2,以上是用简便方法计算的!请点击右下角采纳,