Henry and walter open savings accounts at the same time. henry invests $6,500 at 4.54% simple interest, and walter invests $7,100 at 4.74% simple interest. after eight years, how much more interest has walter earned than henry?

The interest of money placed into investment that has a simple interest can be calculated through the equation,
                              I = Prn
Where I is the interest, P is the principal, r is the decimal equivalent of the given rate and n is the number of years. 

For Henry,
                        I = 6,500 x 0.0454 x 8 = 2360.8
For Walter,
                        I = 7,100 x 0.0474 x 8 = 2692.32
The difference between the calculated interests is 331.52. Thus, after 8 years, Walter will earn $331.52 in interest than Henry.