Answer:
Microeconomics  - The effect of a cigarette tax on the quantity of cigarettes sold
Microeconomics  - The effects of the Internet on the pricing of used cars
Macroeconomics  - The government's decision on how much to spend on public  projects
Explanation:
Microeconomics is the study of the economic action of individual economic agent or unit like individuals, household and the firm., it studies individual income, prices, and wages.
Macroeconomics is the study of the economic as a whole, it is the study of aggregates, like aggregate demand, aggregate supply, national income, inflation, population, exchange rate, interest rate, unemployment, e.t.c.