Answer:
75% brown, 25% white
Step-by-step explanation:
This question involves a single gene coding for color in chickens. The allele for brown color (B) is dominant over the allele for white color (b).
According to this question, a brown rooter with genotype 'BB' was crossed with a white hen (bb). The offsprings in the F1 generation will all possess the 'Bb' genotype and be brown colored. However, if these F1 offsprings are self-mated i.e Bb × Bb, the proportion of F2 offsprings will be 1BB, 2Bb, 1bb.
Since BB, Bb and Bb offsprings are Brown in color and bb is white in color, this means that the expected phenotypic appearance of the F2 offsprings will be:
¾ or 75% brown and ¼ or 25% white