Step-by-step explanation: we know that he starts with 3 lbs of burger meat, and uses some of the meat to make 6 burgers that each weigh 3/8 lbs. If you take the 3/8 lbs and multiply by 6 burgers, you get 18/8, which is how much has been used so far. If you subtract 18/8 from the 3 lbs that Luis has originally started with, you get 6/8 lbs, which is how much he has after his first 6 burgers. Then you can take the 1/4 and see how many times it fits into 6/8 (1/4=2/8, 6/8 divided by 2/8 = 3 burgers that each weigh 1/4 lbs)
