In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.

[EX Q]: Economists divide resources into _ basic categories of land, labor, capital, and management.
[EX A]: four

[EX Q]: Humans brains are about _ times bigger than in chimpanzees.
[EX A]: three

[EX Q]: Many dogs show no problems until they are _ to eight years old or older.
[EX A]:
six