Answer;
q = 80 percent
Explanation;
If a trait has two alleles, p and q, and p is 20% then we can find the percent of q.
According to the Hardy-Weinberg equilibrium;
p+q = 1
Therefore;
q = 1 - p
but; p = 20% or 0.2
Thus; q = 1 - 0.2
= 0.8
The percent of q is 80%