Step-by-step explanation:
As the given reactions are as follows.
Step 1:
(fast)
Step 2:
(slow)
As it is known that a reaction that occurs slowly helps in determining the rate of a reaction.
So, to find overall reaction we will add both step 1 and step 2 by cancelling out common species as follows.
Step 1 + 2 =
![NO + O_(2) + NO_(3) + NO \rightarrow 2NO_(2) + NO_(3)](https://img.qammunity.org/2020/formulas/chemistry/college/9illy0lfv3t5ojupko5brftosuyd1pce5n.png)
Hence, by cancelling the common species the overall reaction is as follows.
![2NO + O_(2) \rightarrow 2NO_(2)](https://img.qammunity.org/2020/formulas/chemistry/college/45ik7b1ltu5txbup3npw4ooxwtwm3nlsqw.png)