The answer is 19
First you must set up the equation
÷
First, you must make the mixed number a improper fraction
÷
Then you must divide

Finally, simplify
19
Given :
Nathan smiled at 50 people one day and recorded that 36 people smiled back at him.
To Find :
How many people should Nathan expect to return a smile if he smiles at 650 people over a period of time.
Solution :
Ratio of people smiled by total number of people is :

Now, it is given that we have to use the given conditions.
Therefore, ratio will be same :

Therefore, number of smiles Nathan expect to return is 468.
The constant rate of change is 5 because