To solve this question, the user needs to know basic arithmetic and the concept of fractions. We can start by adding the fractions that represent the proportion of teams from Europe, the US, and Africa:
20% = 1/5 (Europe)
1/2 (US)
1/20 (Africa)
To find the fraction of teams from neither Europe, the US or Africa, we need to subtract the sum of these fractions from 1 (which represents the total proportion of teams):
1 - (1/5 + 1/2 + 1/20) = 1 - (8/20) = 12/20
Simplifying 12/20 to lowest terms, we get:
12/20 = 3/5
Therefore, the fraction of teams from neither Europe, the US or Africa is 3/5.
Option B (15/20) is incorrect because it is the same as 3/4, which is not equal to 3/5.
Option C (13/15) is incorrect because it is greater than 1 (the total proportion of teams).
Option D (17/20) is incorrect because it is greater than 1 (the total proportion of teams).
The Answer is: A (13/20).