Answer:
The decision to let supply and demand determine the prices of gasoline.
Explanation: A mixed economy is an economy where the socialism ( government ownership and control of businesses) and capitalism( Where private individuals and entities take ownership of businesses). Most economies are mixed where government take certain parts of the control of businesses activities.
If the government allow the forces of demand and supply to set and determine the prices of gasoline and other goods and services it will make the Australian economy less of a mixed economy and more like a pure economy.