Example
The demand for cookies follows the equation: `Q_d = 10 - P`
If price is $3, the quantity demanded is `Q_d = 10 - 3 = 7` cookies.
Question
The demand for cookies follows the equation: `Q_d = 156 - 3 \times P`.
If cookies were sold on the market for $30, what is the quantity demanded?
Plug the price $30 into the demand function:
`Q_d = 156 - 3 \times P = 156 - 3 \times 30 = 66`.