the genotype of the mother must be bl/bl
your answer should explain why this must be so ( cos anything else would not be blue eyed)
the fathers genotype could be br/br OR br/bl
because both genotypes give the same phenotype - brown eyes
then do a mother meets father type diagram with four kids
representing all the possible combinations
you need two diagrams because the fathers genotype has two possibilities
and then you will see with one of the diagrams it is not possible to get blue eyed children and so the genotype has to be second one
where the mother is homozygous for blue and the father is heterosygous
Not bad for a biology question
I always found genetics interesting