Which one is the lowest number?

Is the number 128.439 a rational number

Can someone me find the original price? the discount is 5% and the sale price is $68.40

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