Well for these types of questions the easiest thing to do is to divide them by 10, or 100. The more zeros you add to the denominator, the decimal will move with the same number to the right in the numerator.

3.6= 36/10 = 18/5

4.5= 45/10 = 9/2

7.25= 725/100 = 145/20 = 29/4

3.6= 36/10 = 18/5

4.5= 45/10 = 9/2

7.25= 725/100 = 145/20 = 29/4