This is an incomplete question, here is a complete question.
Consider the following reaction:

In the first 22.0 s of this reaction, the concentration of HBr dropped from 0.590 M to 0.465 M . Calculate the average rate of the reaction in this time interval.
Answer : The average rate of reaction is, 
Explanation :
The given chemical reaction follows:

The average rate of the reaction for disappearance of HBr is given as:
![\text{Average rate of disappearance of HBr}=-\frac{\Delta [HBr]}{\Delta t}](https://tex.z-dn.net/?f=%5Ctext%7BAverage%20rate%20of%20disappearance%20of%20HBr%7D%3D-%5Cfrac%7B%5CDelta%20%5BHBr%5D%7D%7B%5CDelta%20t%7D)
where,
= final concentration of HBr = 0.465 M
= initial concentration of HBr = 0.590 M
= change in time = 22.0 s
Putting values in above equation, we get:

Hence, the average rate of reaction is, 