a,
Gọi x, y là mol $NaCl$, $NaBr$
$\Rightarrow 58,5x+103y=5,5$ (1)
$Cl_2+2NaBr\to 2NaCl+Br_2$
$\Rightarrow n_{NaCl(B)}=x+y(mol)$
$\Rightarrow 58,5x+58,5y=4,3875$ (2)
(1)(2)$\Rightarrow x=0,05; y=0,025$
$C\%_{NaCl}=\dfrac{58,5.0,05.100}{100}=2,925\%$
$C\%_{NaBr}=\dfrac{103.0,025.100}{100}=2,575\%$
b,
$NaCl+AgNO_3\to AgCl+NaNO_3$
$NaBr+AgNO_3\to AgBr+NaNO_3$
$\Rightarrow n_{AgNO_3}=x+y=0,075 mol$
$V_{dd AgNO_3}=\dfrac{0,075.170:20\%}{1,12}=55,92ml$