Oscar is training to compete in a cross country meet at his school. In a week he runs a total of 7 miles in 84 minutes. What is the unit rate of minutes per miles?

To find the unit rate of minutes per mile, divide the total number of minutes by the total number of miles.

Unit rate of minutes per mile = 84 minutes / 7 miles = <<84/7=12>>12 minutes/mile. Answer: \boxed{12}.