Answer:
Sam needs 15 for four people. But, he doesn't have four people, he has ten. So, I multiplied 4x2 and did 15x2 as well. I got 8 people and 30 ounces. He still does not have enough for 10 people. Then, I divided 15 by 4 and got 3.75. This means that 3.75 is enough for 1 person. I then added 3.75 and 3.75 since there are two people left. I got 7.5. After, I added 30 ounces, since that is for eight people, and added 7.5 ounces, which is for two people.
