Solution :
In the question, it is given that :
There are 50 percent yellow winged butterflies and 50 percent black winged butterflies.
The sampled population of the butterflies follows the Hardy-Weinberg equilibrium.
Therefore,
[tex]p+q=1[/tex]
[tex]p^2+pq+q^2=1[/tex]
[tex]$q^2 = \frac{50}{100}$[/tex]
[tex]$q^2 = 0.5$[/tex]
[tex]$q=0.707$[/tex]
So, [tex]p=1-0.707[/tex]
[tex]p = 0.293[/tex]
Therefore, the allele frequency for yellow winged butterflies will be q = 0.707