Answer: 19 years
Step-by-step explanation:
Given
Amount invested 
Rate of interest 
after 1-year amount becomes

After n years it is

Sum accumulated is 

There's a key problem in this question compelling you to actually rewrite it like that! Mathematically that is inaccurate and incorrect. If you do 72(8+19) it seems as if you are going to do 8+19*72 as in algebra whatever is outside the bracket is bound to go multiplied so technically (8+19)+72 would make more sense and the answer is
Using bidmas do the brackets first
8+19= 27
27+72=99
He earned $325 because 900 divided by 4% = $225! :)