Calculate_price is only adding strings and returning the wrong value.

TICKET_PRICE = 10
SERVICE_CHARGE = 2

tickets_remaining = 100

#Creat the calculate price function. It takes ticket amount and returns
#   ticket amount * ticket price
def calculate_price(qty_of_tickets):
    return qty_of_tickets * TICKET_PRICE + SERVICE_CHARGE



while tickets_remaining >= 1:
    print("There are {} tickets remaining.".format(tickets_remaining))
    name = input("What is your name?   ")
    ticket_amount = input("Hello {}, how many tickets would you like?   ".format(name))
    try:
        ticket_amount = int(ticket_amount)
        if ticket_amount > tickets_remaining: 
            raise ValueError("We only have {} tickets available.".format(tickets_remaining))
    except ValueError as err:
        print("Uh-Oh, something went wrong. {} Please try again.".format(err))
    else:
        total_cost = calculate_price(ticket_amount)
        print("The total cost due is {}".format(total_cost))
        buy_or_not = input("Would you like to proceed?  Y/N  ") 
        if buy_or_not.lower() == "y":
            #TODO: Gather credit card information and process it.
            print("SOLD!")
            tickets_remaining -= ticket_amount
        else:
            print("Your order has been cancled. Thank you, {}!".format(name))
print("We just sold out!!")