Answer:
The annual interest rate of return during his investment was 12.28%.
Explanation:
Since Julio purchased 1,700 shares of a certain stock for $ 23,750 including commissions, and I have sold the shares 3 years later and received $ 32,500 after deducting commissions, to find the effective annual rate of return on his investment over the 3-year period the following calculation must be performed: 
 
23,750 = 100 
32,500 = X 
32,500 x 100 / 23,750 = X 
3,250,000 / 23,750 = X 
136.84 = X 
 
(136.84 - 100) / 3 = X 
36.84 / 3 = X 
12.28 = X 
 
Therefore, the annual interest rate of return during his investment was 12.28%.