Possum Poles (Algebra Question)

This is what one of my questions for Possum Poles (Algebra),The character Peta had done in 9 minutes to get to 18 metres and 20 metres would me 10 minutes.

The table has 2 sides, Metres, & Minutes. The minutes only go up to 9 minutes, and the metres only go up to 18 metres but it would Peta 9 minutes & 50 seconds to make it to 20 metres.