Final answer:
Using the simple interest formula and the given monthly interest and annual rate, the principal at the beginning of July for Evander Holyfield's account was calculated to be $12,400.
Step-by-step explanation:
To calculate the principal Evander Holyfield had at the beginning of July, based on the interest for that month, one can use the simple interest formula: Interest = Principal × Rate × Time. We are given that the July interest is $155 and the annual interest rate is 15%. Since the interest given is for one month, the time in the formula would be 1/12 (when the time is in years).
Therefore, we can rearrange the formula to solve for the principal: Principal = Interest / (Rate × Time). Plugging in the numbers, we get Principal = $155 / (0.15 × 1/12). After calculation, the principal comes out to be $12,400.