You want to buy a pet rabbit that costs ​$49. You already have ​$18 and you plan to save ​$9 per week. If w represents the number of weeks until you have enough money to buy the rabbit​, what equation could you use to find the value of​ w? Use pencil and paper. Explain how you could set up an equation to find the amount of money you should save each week if you want to buy the rabbit in six weeks.