I don't know what is wrong


def rental_car_cost(days):
    cost = 40 * days
    if days >= 7:
        cost == -50
    elif days >= 3:
        cost ==  -20
        return cost



You want to remove money from cost for the discount, right? First, we do not set the value of a variable with == this is a comparison sign. Second, we do not set the value of cost to a negative one because we don't want the traveler to receive money from renting the car (you know what I mean), we want him to pay us for renting the car. Here's how you can do it:

cost -= 20 #This is just an example where the discount is 20


Thanks! It worked.!!!!!