You should use a Punnett Square for this question
The Punnett square predicts the offspring of two parents (two alleles). In this case you have brown eyes (Bb) and blue eyes (bb)
In the four boxes you should have Bb, Bb, bb and bb (50% chance of offspring with blue eyes and 50% chance of offspring with brown eyes).
The genotypes ratio will be 2Bb:2bb
And the phenotypic ratio will be 2 Brown : 2 Blue