So P stands for principle which is the amount of the original investment, R stands for rate which is the percent but must be turned into a decimal, T stands for time for example if the time was in a certain amount of months then you plug that in with x/12, and lastly I stands for interest which is the original investment outcome ^_^
The numbers should be less than the denominator, therefore i think it's 5/9 , because the rest have a numerator greater than the denominator, even the 3 . it's written as 3/1 and 3 >1.
