demand funtion for a commodity is=12-3p.

To determine the demand function for a commodity, we need to know the relationship between the quantity demanded and the price of the commodity. In this case, the demand function for the commodity is given as:

Q = 12 - 3P

where:
Q represents the quantity demanded of the commodity
P represents the price of the commodity

This equation shows that as the price (P) of the commodity increases, the quantity demanded (Q) decreases. Conversely, as the price decreases, the quantity demanded increases.

To find the demand function, you need to have information on the quantity demanded at different price levels. Once you have the quantity demanded for at least two different prices, you can create a table or graph to determine the equation for the demand function.

Let's consider an example with two data points:

Price (P): 1 unit
Quantity demanded (Q): 9 units

Price (P): 3 units
Quantity demanded (Q): 3 units

With these two data points, we can find the equation for the demand function by substituting the values into the equation:

For the first data point:
9 = 12 - 3(1)
9 = 12 - 3
9 = 9

For the second data point:
3 = 12 - 3(3)
3 = 12 - 9
3 = 3

Based on these calculations, we can see that the equation Q = 12 - 3P satisfies the given data points. Therefore, the demand function for the commodity is Q = 12 - 3P.