Em tham khảo nha :
\(\begin{array}{l}
a)\\
\left\{ \begin{array}{l}
2{p_A} + {n_A} = 115\\
2{p_A} - {n_A} = 25
\end{array} \right.\\
\Rightarrow {p_A} = 35,{n_A} = 45\\
b)\\
{n_2} = {n_1} + 2 = 45 + 2 = 47\\
{A_1} = 35 + 45 = 80\\
{A_2} = 35 + 47 = 82\\
\% {A_2} = 100 - 50 = 50\% \\
{M_{tb}} = \dfrac{{80 \times 50 + 82 \times 50}}{{100}} = 81g/mol
\end{array}\)
