Final answer:
The total change in field position for the football team is 0 yards, after adding the yards gained and subtracting the yards lost from the three plays.
Step-by-step explanation:
The student is asking about calculating the total change in field position for a football team after three plays. To compute the total yardage, you take the sum of the yards gained and lost during the plays. The first play gained 15 yards, the second lost 12 yards, and the third lost 3 yards. Adding these together, the total change in field position is 15 yards - 12 yards - 3 yards which equals 0 yards.
Today, a yard is a standardized unit of measurement that is used consistently across football fields, which means that no matter where the game is played, the field is marked with the same yardage. This wasn't always the case historically, as the yard was once defined by the length from the king's nose to his outstretched hand, which could vary with each new king.