Which value is the opposite of 7 on a number line?

Explanation

Opposites share a magnitude and differ only in sign, so the opposite of a value of size seven is the value of size seven carrying a minus sign. Offering 7 itself changes neither the size nor the sign, and only zero, which has no sign to reverse, equals its own opposite. The value -14 doubles the size as well as reversing the sign, which taking an opposite never does.