What does it mean when two functions are inverse of each other?

Which of the following points is collinear with (-2,1) and (0,3)

Adam used 1072.4 gallons of water over the course of 7 days. how much water did adam use, on average, each day?

When you dilate a figure with a scale factor of 1/2, what will the dilated figure look like?                                                                                           a: the dilated figure will have side lengths that are half the length of the original side lengths.                                                                          b: the angles in the dilated figure will be half the measure of the original figure.                                                                                c: the dilated figure will have side lengths twice the length of the original.