Let Qd306p and Qs 9p Equilibrium combination is p10 q90 or

Let Qd=30-6p and Qs =9p , Equilibrium combination is p*=10; q*=90 or p*=2;q*=18 or p*=18; q*=2 or p*=2; q*=15

Solution

At equilibrium

Qd = Qs

30 - 6p = 9p

15p = 30

p^* = 2

Setting value of the equilibrium price in the supply function we get,

q^* = 9*2 = 18

Thus, equilibrium combination is p*=2;q*=18