Answer
See the answer below.
Work Step by Step
a) The concentration of CO and Cl2 reacted from each: x
The concentration of COCl2 formed: x
The concentration of Cl2 at equilibrium is $0.00301\ M=0.00609\ M-x\rightarrow x=0.00308\ M$
At equilibrium then, $[COCl_2]=0.00308\ M, [CO]=0.0102\ M-0.00308\ M=0.00712\ M$
b) $K=[COCl_2]/[Cl_2][CO]$
$K=0.00308/0.00712/0.00301=143.2$