(x×40%+5)+【(x×40+5)】×80%=12

(x×40%+5)+【(x×40+5)】×80%=12
(x×40%+5)+【(x×40+5)】×80%=12

(x×40%+5)+【(x×40+5)】×80%=12
(x×40%+5)+(x×40+5)×80%=12
（0.4x+5）+（32x+4）=12
32.4x+9=12
32.4x=3
x=0.09

(0.4x+5)+0.8(0.4x+5)=12
(1+0.8)(0.4x+5)=12
0.4x+5=12÷1.8
0.4x+5=20/3
0.4x=20/3-5=5/3
x=5/3÷0.4
x=4又6分之1