You want to buy a pet lizard that costs ​$45. You already have ​$14 and you plan to save ​$7 per week. If w represents the number of weeks until you have enough money to buy the ​, what equation could you use to find the value of​ w? 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 lizard in 3 weeks.