Chapter 5 - Number Theory and the Real Number System - 5.2 The Integers; Order of Operations - Exercise Set 5.2 - Page 271: 145

This answer makes sense.

By subtracting a record low (a negative number) from a record high temperature (a positive integer), we get the variation in temperature. For example, if the record low for a particular day is -12 degrees and the record high for the day is 46 degrees, we can subtract 46 - (-12), we actually add 46 and 12 to get 58. The difference in the temperatures gives us the variation in temperature for that day. In a little more detail if we start with a record low of -12 and a record high of 46, we find the difference between the two by looking at a number line (or thermometer). To get from-12 to 0, we move 12 units (degrees). Them from 0 to 46, we move 46 more units. When we combine those values, we get 58.