Substitute the E line into the Kp expression and solve for x, 319-x, and 220-x. Then add mols of each to find total mols.
XCO = nCO/total mols
XCl2 = nCl2/total mols
XCOCl2 = nCOCl2/total mols.
The problem only asked for XCOCl2 but all of them can be calculated easily after you have the first one.