$\therefore \text { Molality }=\frac{2 / M _{ A }}{0.098}$

For $B$ : $100\,gm$ solution $\rightarrow 8\,gm$ solute $B$

$\therefore \text { Molality }=\frac{8 / M _{ B }}{0.092}$

$\because\left(\Delta T _{ B }\right)_{ A }=\left(\Delta T _{ B }\right)_{ B }$

$\therefore$ Molality of $A=$ Molality of $B$

$\therefore \frac{2}{0.098 M _{ A }}=\frac{8}{0.092 M _{ B }}$

$\frac{2}{98} \times \frac{92}{8}=\frac{M_{A}}{M_{B}}$

$\frac{1}{4.261}=\frac{ M _{ A }}{ M _{ B }}$

$\therefore M_{B}=4.261 \times M_{A}$