Answer: 80 - 85% of the world.
Step-by-step explanation:
At the height of European colonization, most of the world (80%+) had been colonized by the ambitious nations of Europe. Britain in particular, ruled almost 25% of the world at the height of their empire which would make them the largest empire to have ever existed.
Other European nations that coloniser vast areas are Spain, Portugal and France. The effect of this is that most of the world speaks a European language or another as their official language.