Final answer:
The external costs of smoking equal social costs plus private costs.
Step-by-step explanation:
The external costs of smoking are equal to social costs plus private costs. In economic terms, external costs refer to the costs incurred by third parties outside the production process.
These costs can include health care expenses for treating smoking-related illnesses and the costs of pollution caused by smoking.
Private costs, on the other hand, are the costs incurred by the individuals or firms involved in the production or consumption of cigarettes.