17. x+y=314,2/3x=4/5y-40
16 . x=1/6y, x+15=(y+15)*4/9
15.x+y+z=1760,x*(1-2/9)=y+80=z
14.30%x/(x+24)=25%
13.(.x-1/5x)(x+4)=x^2
12.100*(1-66%)/(1-15%)
混俩没篙冰
17. x+y=314,2/3x=4/5y-40
16 . x=1/6y, x+15=(y+15)*4/9
15.x+y+z=1760,x*(1-2/9)=y+80=z
14.30%x/(x+24)=25%
13.(.x-1/5x)(x+4)=x^2
12.100*(1-66%)/(1-15%)
混俩没篙冰