[tex]Percentage=Rate*Base \\ Rate= \frac{Percentage}{Base} [/tex]
In this problem we are looking for the rate since you are asking what percent.
In this problem the percentage is 45 and the base is 200. In order to know which is the base we look for the keyword of.
[tex]Rate= \frac{45}{200} =0.225[/tex]
We multiply this by 100 since we want the rate or percent (%) and percent means per 100.
So the rate is 22.5%