Two solids dissociate as follows: A(s) ⇌ B(g) + C(g); K _ P _ 1 = x...

${k}_{{p}_{1}} = {P}_{1}\left({P}_{1} + {P}_{2}\right)$

${k}_{{p}_{2}} = {P}_{2} ( {P}_{1} + {P}_{2} )$

${k}_{{P}_{1}} + {k}_{{P}_{2}} = {( {P}_{1} + {P}_{2} )}^{2}$

$x + y = {( {P}_{1} + {P}_{2} )}^{2}$

${P}_{1} + P{}_{2} = \sqrt{x + y}$

$2 ( {P}_{1} + {P}_{2} ) = 2\sqrt{x + y}$

${P}_{Total} = {P}_{B} + {P}_{C} + {P}_{E}$

$= 2 ( {P}_{1} + {P}_{2} ) = 2\sqrt{x + y}$