Final answer:
To find out how many pupils support Arsenal, we need to subtract the number of pupils supporting Chelsea from the total number of pupils. Since we don't know the exact number of pupils supporting Chelsea, we can't determine the number of pupils supporting Arsenal with the given information.
Step-by-step explanation:
In this question, there are 25 pupils in the class and some support Chelsea while the remainder support Arsenal. To find out how many pupils support Arsenal, we need to subtract the number of pupils supporting Chelsea from the total number of pupils.
If we let x represent the number of pupils supporting Chelsea, then the number of pupils supporting Arsenal is 25 - x.
Since we don't know the exact number of pupils supporting Chelsea, we can't determine the number of pupils supporting Arsenal with the given information.