Qd = 170 – 20P and P = 4, at equilibrium

✅ Explanation: At equilibrium, quantity demanded (Qd) equals quantity supplied (Qs). We are given Qd = 170 – 20P and P = 4.
Substitute P = 4 into the demand equation: Qd = 170 – 20 * 4 Qd = 170 – 80 Qd = 90
Since Qd = Qs at equilibrium, then Qs = 90.