Think of two houses. If we say "the houses are identical" then the corresponding pieces must be the same (eg: the doors must be the same type out of the same material). In this analogy, the houses are the triangles, which are the overall structures. The doors are the angles since they are pieces of the overall structures. This is what CPCTC is saying
CPCTC = Corresponding Parts of Congruent Triangles are Congruent
First, you want to add together the amount of money she spent on purses ($24), and then consider the amount of scarves (5+n). To solve, you would subtract 24 from 39, and then divide that answer by 5