12 inches in this circle represents its

I can't see the whole picture, but if it's half of the circle, it's the radius. if the line goes all the way through the circle, it's the diameter

question: how many people can she serve?

answer: she can serve 16.66666667 people. so she can only give 16 people a complete serving.

question: does she have enough ice cream for her guests?

answer: no. explanation: she only has enough for 16 people to have a full serving. however, she can give a 17th person a partial serving.