Final answer:
To calculate the percentage of Social Security benefits excluded from gross income, subtract the total deductions percentage from 100%.
Step-by-step explanation:
To calculate the percentage of Social Security benefits excluded from gross income, we can use the information given in the question. Since the question does not specify the exact amount of Social Security benefits received, we'll assume it to be $X. According to the information provided, the deductions for Social Security, Medicare, and taxes are 6.2%, 1.45%, and 15% of the gross annual income, respectively. Therefore, the total deductions would be 6.2% + 1.45% + 15% = 22.65%. So, the percentage of Social Security benefits excluded from gross income would be 100% - 22.65% = 77.35%.