Which development allowed the jamestown colony to develop a viable economy?

The headright rule that encouraged indentured servitude.

Explanation:

One of the most important developments in the colonies was the concept of a headright system. This system was first developed in Jamestown, Virginia in 1618 as a way to attract more settlers to the area. This system gave new settlers 50 acres of land. As most settlers became indentured servants, this also addressed the labor shortage in the colonies and allowed the tobacco industry to become profitable.

might be agreeing to participate ethically with other european nations in the slave trade

or notifying other european nations when taking possession   of african territories

it increase by 12% a year from 1812-1820