9 , 10 ,11 nhé anh em, giúp tôi nhé cảm ơn

9/ 189 = $\frac{10.18,89%+A2.a2}{100}$ 

189+A2.a2=1081

⇔A2.81,11%=1081-189=892

⇔A2=892/81,11≈11(amu)

10/107,88=$\frac{109.44%+A2.56%}{100}$ 

4796+A2.56%=10788

⇔A2.56%=10788-4796=5922

⇔A2=5922/56%=107(amu)

11/$\left \{ {{a1+a2=100} \atop {63.a1+65.a2=6354}} \right.$ 

⇔$\left \{ {{65.a1+65.a2=6500} \atop {63.a1+65.a2=6354}} \right.$ 

⇔$\left \{ {{2a1=146} \atop {a1+a2=100}} \right.$ $\left \{ {{a1=73} \atop {a2=100-73=27}} \right.$ 

vậy a1=73%. a2=27%