In 12 cups of flour,we are going to have 2 cups of flour in six(6) places.
Thus, for 12 cups of flour, Mrs Smith will use:
[tex]\begin{gathered} \frac{3}{8}\times6\text{ cup of chocolate chips} \\ \Rightarrow\frac{18}{8}=\frac{9}{4\text{ }}cup\text{ of chocolate chips} \end{gathered}[/tex]