#2A(g) + B(g) rightleftharpoons C(s) + 3D(g)#
As you can see from the values of the equilibrium constant, the #K_(eq)# has decreased after heating (#2.3xx10^2<4.2xx10^3#).
Since the expression of #K_(eq)# is:
#K_(eq)=([D]^3)/([A]^2[B])=(["Products"])/(["Reactants"])#
If the value of #K_(eq)# has decreased, this means that the concentration of products (numerator) has decreased as well, which implies that products were consumed during the process, therefore, the reaction has proceeded in the reverse direction .
According to Le Châtelier's principle , for an exothermic reaction, when heat is added, the reaction will proceed in the reverse direction since heat is considered one of the products:
#2A(g) + B(g) rightleftharpoons C(s) + 3D(g)+color(red)(Heat)#
