Let molar mass of protein $B = y g / mol$

$\pi_{ A }=$ osmotic pressure of protein $A =\frac{\left(\frac{0.73}{ x }\right)}{0.25} RT$

$\pi_{ B }=$ osmotic pressure of protein $B =\frac{\left(\frac{1.65}{ y }\right)}{1} RT$

$\pi_{ A }=\pi_{ B }$

$\Rightarrow\left(\frac{0.73}{ x \times 0.25}\right) RT =\left(\frac{1.65}{ y }\right) RT$

$\Rightarrow\left(\frac{ x }{ y }\right)=\frac{0.73}{0.25 \times 1.65}=1.769 \cong 1.77$