In mice, the allele for black fur is dominant to the allele for brown fur. a male homozygous black mouse is crossed with a female brown mouse, and the f1 offspring are allowed to breed. what proportion of the black mice in the f2 offspring do you predict will be homozygous? ( enter the number only without the percent sign. for example, enter 100% as 100 and enter 12.5% as 12.5 )

B- black allele;
b- brown allele;

The parental cross is true-breeding because both the male and the female are homo zygotes, so: BBx bb

The F1 generation will be all black heterozygote: Bb
The F2 generation will be between mice of the F1 generation and they all have the same genotype:Bb xBb
In this cross it would result in:
 1/4 of the plants being black homozygote-BB 25%
2/4 of the plants being black heterozygote- Bb- 50%
1/4 of the plants being  brown homozygote- bb- 25%
25%+25%=50%  are homozygotes