Assume the demand curve for concert tickets is Qd= 300 - c*p and the supply curve is Qs= p - 20 (quantity expressed in thousands of tickets)
What is the equilibrium price and quantity
What are the consumer surplus and the producer surpluses.
Is "c" in your demand equation an unspecified parameter?
Anyway, set Qd=Qs and solve for p. With p, solve for Qd. Consumer surplus is the area of the triangle above price but below demand. Producer surplus is the area of the triangle below price but above supply.