Подчеркните герундий одной чертой и инфинитив двумя чертами. 1) when planning his expenditure an individual must accept the fixed prices of the commodities he wants. 2) an economic model often helps an economist to make correct prediction. 3) the role of the company in the free market is to supply what people want.
2) An economic model often helps an economist "to make- инфинитив" correct prediction.
3) The role of the company in the free market is "to supply - инфинитив" what people want.