If you have quantity demanded(Qd) and quantity supplied(Qs) then you can calculate equilibrium price and quantity.  To find equilibrium price and quantity you have to find equilibrium point(EP).


EP=> Qd=Qs

suppose, Qd=100-2p &Qs=4p-80

EP=>100-2p=4p-80
   =>-2p-4p=-80-100
   =>-(2p+4p)=-(80+100)
   =>2p+4p=80+100
   =>6p=180
   =>p=180/6=30

so, equilibrium price is 30

and equilibrium quantity is, Qd=Qs … Read more