91影视

Two numbers with similar signs get added and the resulting number carries the similar sign.

Two numbers with opposite signs get subtracted and the resulting number carries the sign of the larger number.

The distance above the sea level is measured in positive, while the distance below the sea level is measured in negative.

Since the lowest point of the highway is 110 feet below the sea level, so the integer that represent the elevation of the lowest point of the highway is 鈥�110.

And the lowest point of the tunnel is 90 feet below the sea level, so the integer that represent the elevation of the lowest point of the tunnel is 鈥�90.

To evaluate the difference of $-110\text{and}-90$, we will add the opposite of the second number with the first number. That is, add the opposite of 鈥�90 with 鈥�110.

To subtract $-90$, add its opposite 90 with the first number to get

Thus, the difference of the numbers is $-20$.