F4 Economic-equilibrium price

I'm afraid that you have misundered of equilibrium!!
首先~
要有一個較為清晰的concept在腦裡面,
demand is not equal to quantity demanded(QD)
and supply is not equal to quantity supplied(QS)
change in demand係會shift leftwards when demand decreases.
Vice versa,shift rightwards when demand increases.
change in supply都係一樣,成條curve shift leftwards就係decrease in supply,
shift rightwards 就係increase in supply
而change in QD就係along the same demand curve
change in QS都係一樣,係along the same supply curve
equilibrium就係QD=QS ,and no tendency for the price and quantity transacted to changed.

Demand and supply are two different entities(things) so the two can never be equal.

You may say that equilibrium price is
the price at which the quantity demanded and the quantity supplied are equal.