Answer: Decrease in the quantity demanded.
Step-by-step explanation:
According to the law of demand, other things remains constant, if there is increase in the price of a commodity as a result the quantity demanded for that commodity decreases.
In this case, McDonalds increases the price of its hamburgers, so as a result the quantity demanded for the hamburgers decreases. This is due to the higher prices as it will be more expensive for the consumer to buy hamburgers at the prevailing prices.