Cho hệ $\left\{ \begin{array}{l} 72a+232b+160c=7,68(1)\\ 2a+8b+6c=0,26 \end{array} \right.$
Có $2a+8b+6c=7,68$$\Rightarrow 72a+288a+216c=9,36(2)$
Lấy $(2)-(1) \Rightarrow 56b+56c=1,68$
$\Rightarrow b+c=0,03$
Mặt khác có $\frac{160}3a+\frac{640}3b+160c=\frac{104}{15}(3)$
Lấy $(1)-(3) \Rightarrow \frac{56}3a+\frac{56}3b=\frac{56}{75}$
$\Rightarrow a+b=0,04$
Xét $a+3b+2c=(a+b)+2(b+c)=0,04+2.0,03=1$