Chapter 3.4, Problem 11P

Denise says that $\frac{2}{3}-\frac{1}{2}=\frac{1}{3}$ and gives the reasoning indicated in Figue 3.31 to support her answer. Is Denise right? If not, what is wrong with her reasoning and how could you help her understand her mistake and fix it? Don’t just explain how to solve the problem correctly; explain where Denise’s reasoning is flawed.

 

   Figure 3.31 Denise’s idea for $\frac{2}{3}-\frac{1}{2}$ .