Margie would take 1 hour and 30 minutes to write 1 page of her research paper. Think of it like a proportion:
2.25/ 1.5 = x/1
2.25 is the 2 1/4 converted which is the amount of hours she took.
1.5 is the 1 1/2 converted which are the amount of pages she wrote total.
1 on the right side of the proportion represents 1 page.
And x are the amount of hours used to write 1 page.
And in solving that proportion it would result in 1.5 or 1hr. and 30 min.