Kc = [CS2] / [S2][C] but, since C is solid, it doesn't fit here
Kc = [CS2] / [S2]
S2(g) + C(s) ---> CS2(g)
13.8mole S2 / 6.05L = 2.28M
Kc = x / 2.28-x
9.4 x (2.28-x) = x
21.43 - 9.4x = x
21.42 = 10.4x
x = 2.05M = [CS2]
2.05M x 6.05L = 12.46moles
12.46moles x 76gmole = 946.96g CS2