To find a relative date by adding 10 weeks to a specific date, such as 27th July, one can manually calculate it by breaking it down into steps. First, convert 10 weeks to days, knowing that a week consists of 7 days, so 10 weeks equate to 70 days. Then, add these 70 days to the original date, 27th July. Next, consider the number of days in each month to ensure accurate calculation, accounting for leap years as well. This method allows for precision in determining the correct relative date in the future.