$250\,\, = \,\,P_A^0\left( {\frac{1}{{1\,\, + \,\,2}}} \right)\,\, + \,\,\left( {\frac{2}{{1\,\, + \,\,2}}} \right)\,P_B^0\,\,\,........(1);$
$\,300\,\, = \,\,P_A^0\left( {\frac{2}{{2\,\, + \,\,2}}} \right)\,\, + \,\,\left( {\frac{2}{{2\,\, + \,\,2}}} \right)P_B^0\,\,.........(2)$
$P_A^0\,\, = \,\,450\,\,mm\,\,Hg,\,\,P_B^0\,\, = \,\,150\,\,mm\,\,Hg$