It is clearly mentioned in the question that each bottle of ibuprofen has 1000 pills.
Now, 1/4 bottle of ibuprofen is used to make the prescription.
So, if one bottle of ibuprofen has 1000 pills and 1/4 1/4 bottle of ibuprofen is used to make the prescription, then Jerome obviously used [tex] \frac{1000}{4}=250 [/tex] pills of ibuprofen to make the prescription.
This can be further explained as follows:
1 bottle=1000 pills
[tex] \therefore \frac{1}{4} [/tex] bottle=[tex] \frac{1000}{4} [/tex]=250 pills.