Em tham khảo nha :

\(\begin{array}{l}
a)\\
2A + 2xHCl \to 2AC{l_x} + x{H_2}\\
{B_a}{O_b} + 2bHCl \to aMC{l_{\frac{{2b}}{a}}} + 2y{H_2}O\\
b)\\
{n_{{H_2}}} = \dfrac{{1,344}}{{22,4}} = 0,06mol\\
{n_A} = \dfrac{2}{x}{n_{{H_2}}} = \dfrac{{0,12}}{x}mol\\
{M_A} = 3,9:\dfrac{{0,12}}{x} = 32,5dvC\\
x = 2 \Rightarrow {M_A} = 65dvC\\
 \Rightarrow A:\text{Kẽm}(Zn)\\
{n_{HCl}} = 2{n_{{H_2}}} = 0,12mol\\
{n_{{B_a}{O_b}}} = \dfrac{{{n_{HCl}}}}{{2b}} = \dfrac{{0,06}}{b}mol\\
{M_{{B_a}{O_b}}} = 3,2:\dfrac{{0,06}}{b} = \dfrac{{160}}{3}b\\
a{M_B} + 16b = \dfrac{{160}}{3}b\\
a = 2;b = 3 \Rightarrow {M_B} = \dfrac{{160 - 16 \times 3}}{2} = 56dvC\\
 \Rightarrow B:\text{Sắt}(Fe)
\end{array}\)