0.5x+2x/5=80%-0.08
0.5x+0.4x=0.8-0.08
0.9x=0.72
x=0.72/0.9
x=0.8确定？我写的题目对就确定再问一题 就给20分(4分之3加4分之1÷10分之3）×2 能简便的要简便(3/4+1/4÷3/10)X2 (3/4+1/4÷3/10)X2=(3/4+1/4X10/3)X2=(1/4X9/3+ 1/4X10/3)X2 =(3/4+5/6)X2 =1/4X(9/3+10/3)X2=3/2+5/3=1/2X19/3=9/6+10/6=19/6=19/6(这应该是简便的）