Give the step-by-step reasoning process and then the final answer. Thomas wants to throw a party for his best friend Casey. He needs to order enough chairs for all the party guests to sit in, one for each guest. First he orders 3 dozen chairs for 3 dozen guests he invites. Then he finds out that 1/3 of the guests want to bring a guest of their own, so Thomas needs to order more chairs. Eventually, Thomas finds out that 5 of the guests he originally invited can't make it. Thomas would also like to order 12 extra chairs just in case they need them. How many chairs is Thomas going to order for Casey's party?
Thomas originally orders chairs for 3 dozen guests, 12 x 3 = 36 guests. Thomas finds out that 1 / 3 of the guests want to bring a guest of their own, 1 / 3 of 36 = 12. The 12 guests bring a guest of their own each, 36 guests + 12 guests = 48. Thomas finds out that 20 of the guests can't make it, 48 guests - 5 guests = 43. Thomas wants to order an extra 12 chairs, 43 + 12 = 55. Thomas will need 55 chairs for the party.
The final answer: 55.