In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.
--------
Question: Masturbation tends to peak when children are between the ages of _ and five.

Answer: three

Question: Pelycosaurs are a paraphyletic group of _ primitive families of synapsids.

Answer: six

Question: Microbial inhabitants outnumber our body's own cells by about _ to one.

Answer:
ten