Answer:
1 or 100%
Step-by-step explanation:
Assuming that the allele B (brown) is dominant over the allele b, crossing the father and the mother:
BB x bb
Bb Bb Bb Bb (you can also see the Punnet's square)
All the offspring would exhibit the dominant phenotype which is brown. Hence, the probability of the offspring having brown eyes is 100% or simply 1.