0 represent the sea surface since the dolphin jumped from five feet below the sea surface and since Jane put that the dolphin jumped at -5 below the sea surface that would mean that 0 must represent the sea surface.
There are 130 tickets. 30 of these tickets are worth $5 or $ 10. Therefore, 30 of these 130 tickets are worth $5 or greater. Simplying 30 / 130 gives the probability of 3 / 13 or roughly 23%.