Question

Calculate the equlibrium quantity and price if the quantity supplied can be represented by equation Qs=18000 +0. 2P and quantity demanded can be represented by the Equation Qd=2400-0.1P

Answer 1

The market equilibrium occurs when $Q_d=Q_s$ (it seems that there is a typo in supply function because in this case we get the negative equilibrium price):

$$2400-0.1P_E=1800+0.2P_E,$$ $$0.3P_E=600,$$ $$P_E=\$2000.$$

Then, we can substitute $P_E$ into the demand function and find the equilibrium quantity:

$$Q_E=2400-0.1\cdot\$2000=2200.$$