the first thing to do here is convert it to a mixed number.
.25 should be a somewhat familiar decimal. it's created by the fraction (1/4), so instead of 2.25, you could write this as 2 1/4 (two and one-fourth).
now that you have 2 1/4, convert it to an improper fraction. remember, multiply the bottom of your fraction with the big number out front, then add to the top of your fraction. set it over your denominator.
2 1/4 ... 4*2 is 8, 8 + 1 is 9, and your resulting fraction is (9/4).