The complex, Cr(CO)x obeys EAN rule value of ‘x’ is
If EAN is obeyed the value of EAN of the complex must be equal to atomic number of next higher inertgas.
EAN of Cr(CO)x must be 36.
EAN = ‘Z’ of central metal -oxidation state of metal +2(Coordination number)
36 = 24 - 0 + 2x
x = 6