Chapter 1 - Foundations for Algebra - 1-9 Patterns, Equations, and Graphs - Practice and Problem-Solving Exercises - Page 66: 53

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A key rule to remember is that subtracting a negative is the same as addition. Thus, we know that: $-15-(-14)=-15+14 $ We must also remember that a negative becomes more positive when a positive number is added to it. Thus, we obtain: $-15+14=-1$