I would easily recommend to convert these to decimals. If you don't know how you should search it up or ask a teacher/friend. Convert 2 3/4 to .75, and then 2 1/2 is 2.50. Add 2.75 twice because he is making 2 dozen each (and a half) equals 11. Then multiply the 2.75 by .50 (6 muffins). That is 1.375. Add 11 and 1.375 equals 12.375. I'm not 100 percent sure this is correct but I hope it helps. :)