Question

A football team is on the 35-yard line. The quarterback is sacked at the line of scrimmage. The team gains 0 yards, so they are still at the 35-yard line. Which identity or property does this represent? Explain.

Answer 1

This is called the "Additive Identity Property (of Addition)". Any number plus or minus 0 is still that number.

$x+0 = 0$

$x-0 = 0$

This is reflected in the second equation here.