According to betweenness of points, if points a, b, and c are collinear and ab + bc = ac, then b is between a and c. true or false?

Adolphin is swimming with her friend. the dolphin jumps to a height of 4.54.54, point, 5 meters above the surface of the water as her friend swims 9.89.89, point, 8 meters directly below her. what is the position of the dolphin's friend relative to the surface of the water? meters