What are the first twenty counting numbers in base nine?

Afamily of five rents a kayak and splits the total time, k, equally. each family member spent less than 25 minutes kayaking. which values can be used to complete the math sentence below so that it accurately represents the situation? intro done

The pyramid below was dissected by a horizontal plane which shape describes the pyramid horizontal cross section

See attachment below and find the equivalent of tan(∠qsr)