Answer:
The American population was 20% of the British population.
Step-by-step explanation:
Let us call
the american population,
the British population before the migration, and
the population that migrated from America to Britannia.
Now, the population
that migrated was 20% of the american population:
,
and the same population
increase the British population by 4%:

Combining equation (1) and (2) we get:



Thus, the American population was 20% of the British population.
The percent error is 29%. I posted the equation for percent error on your other question.
Answer:
its a slope....
Step-by-step explanation: