Need with an graph --> equation

Take a look at the two points (0,6) and (4,0). The slope of the line connecting these two points is negative. The slope is -6/4, or -3/2.

Using the point-slope equation of a straight line, the equation applying here is

y - 0 = (-3/2)(x - 4), or y = (-3/2)x + 6

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.