Chickens with white plumage, when crossed, always give white offspring, and chickens with black plumage, black.

Chickens with white plumage, when crossed, always give white offspring, and chickens with black plumage, black. The offspring are white and black, give gray. What part of the offspring from crossing a gray rooster and a chicken will be with gray plumage?

Based on the condition of the problem, we conclude that we are talking about the so-called incomplete dominance, when the presence in the genotype of both the dominant and the recessive gene gives a new, intermediate trait.
Let us designate the gene responsible for the development of the white color of the chicken feathers by the letter A, and the gene for the black color by a.
Black chickens will be designated aa and produce gametes a, white chickens – AA, gametes – A.
Gray chickens – Aa.
When crossing a gray rooster Aa and a gray chicken Aa, which produce eggs and sperm A and a, the offspring will be obtained:
white chickens (AA) – 25%;
gray chickens (Aa) – 50%;
black chickens (aa) – 25%.
Answer: 50% of the offspring of this pair of parent individuals will have gray plumage.