Question

One town is 20 feet above sea level another town is 10 feet below sea level are these opposite quantities who sum is 0

Answer 1

Yes, these are opposite quantities. The first town is 20 feet above sea level, which means it has a positive value of 20. The second town is 10 feet below sea level, so it has a negative value of -10. When you add these two quantities together, 20 + (-10) = 0, the sum is zero.