Answer
Rate law = $k[NO_2]^2$
Overall balanced equation: $NO_2+CO\rightarrow NO+CO_2$
Work Step by Step
The rate law is determined from the slowest elementary step, which is given in the problem. Since the slowest elementary step requires 2 $NO_2$ molecules to collide with each other, the exponent on the concentration of $NO_2$ in the rate law is 2.
The overall balanced equation can be found by adding together the reactions of the two elementary steps given in the problem.
