The coldest day in ohio clocked in at 40 below zero. In one day though the temperature changed to 20 below zero How much temperature change was there that day
40 below 0 would be -40 and 20 below 0 would be -20°. So there’s a change of (increase of) 20° that day. It would also make sense if you drew a number line. You would see the interval between -40 and -20 is 20.