Chapter 1 - Foundations for Algebra - 1-5 Adding and Subtracting Real Numbers - Practice and Problem-Solving Exercises - Page 34: 38

4.6

A key rule to remember is that subtracting a negative is the same as addition. Thus, we obtain: $-2.9-(-7.5)=-2.9+7.5$ We now must recall that a negative becomes more positive when a positive number is added to it. $-2.9+7.5=4.6$