Step-by-step explanation:
When the price of VCRs fall and the price of plastic (used to make videotapes) rise, then there will be an increase in the price and decrease in demand and for videotapes since they are strong compliments.
Consider this analogy, people used to need videotapes in other to record on VCRs; (just a sim card is needed so as to fully use a phone). Hence, as the price of the material (plastic) used to make videotapes rises; ultimately the videotape prices themselves would increase; leading to lesser demand.
As a result of this, we can expect the equilibrium price and quantity to decrease.