Write down the formula to calculate the distance he runs in n-th week
To calculate the distance someone runs in the n-th week, we need to know the distance they run per day and the number of days they run in a week. Assuming the distance per day remains constant, we can use the following formula:
Distance in the n-th week = Distance per day x Number of days in the week
To get the specific values for distance per day and number of days in a week, we would need more information.