Since going to the movies is a substitute for watching a DVD at home, an increase in the price of going to the movies should cause more people to switch from going to the movies to staying at home and renting DVDs. Thus, the demand curve for DVD rentals will shift to the right when the price of movie theater tickets increases [Panel (a)].
A decrease in family income will cause the demand curve to shift to the left if DVD rentals are a normal good but to the right if DVD rentals are an inferior good. The latter may be the case for some families, since staying at home and watching DVDs is a cheaper form of entertainment than taking the family to the movies. For most others, however, DVD rentals are probably a normal good [Panel (b)].
An increase in the price of DVD rentals does not shift the demand curve for DVD rentals at all; rather, an increase in price, say from P1 to P2, is a movement upward to the left along the demand curve. At a higher price, people will rent fewer DVDs, say Q2 instead of Q1, ceteris paribus [Panel (c)].