#2NO_((g))+O_(2(g))rightleftharpoons2NO_(2(g))#
#K_p=(p_(NO_2)^(2))/(p_(NO)^(2)xxp_(O_2))#
#p# represents the partial pressure of the gas.
The relationship between #K_p# and #K_c# is given by:
#K_p=K_c(RT)^(Deltan)#
#R# is the gas constant
#T# is the absolute temperature
#Deltan# is the difference between the no. moles of product molecules - the number of moles of reactant molecules.
In this case you can see that #Deltan=2-3=-1#
#:.K_p=K_c(RT)^(-1)#
#K_p=K_c/(RT)#
#:.K_c=K_pxxRT#
#K_c=2.2xx10^(12)xxRxx298#
#K_c=6.55xx10^(14)R#
You can't evaluate this numerically since no units are given for #K_p# so you can't chose a value for #R#.
