The market demand and supply equations for a product are:
​QD = 30 − 3P
​QS = 20 + 2P
Here, Q = quantity, P = price.

What is the equilibrium demand?

Correct option is C

To find equilibrium demand, we need to determine the equilibrium price first.
At equilibrium:

QD = QS

Substitute the given equations:

30 - 3P = 20 + 2P

Now solve for P (price):

30 - 20 = 3P + 2P

10 = 5P

P = 2

Now substitute P = 2into the demand equationto findequilibrium demand:

QD = 30 - 3(2)

QD = 24

Thus, equilibrium demand = 24 units.

Information Booster:

• Equilibrium in a market occurs when quantity demanded equals quantity supplied.

• Solving the equations simultaneously gives the equilibrium price.

• Substituting the price into either equation gives the equilibrium quantity.

• At equilibrium, there is no surplus or shortage in the market.

• The concept is fundamental in microeconomic market analysis.

• Demand curves are typically downward sloping, and supply curves are upward sloping.

• Equilibrium ensures market efficiency under perfect competition assumptions.