Question

A true breeding brown mouse is mated with a true-breeding white mouse and all their offspring are brown. If two of these brown offspring are mated, what percentage of the F1 and F2 generations will be brown?

Answer 1

If you mean homozygous by "true breeding," Brown is dominant over white, because all of F1 generation are all brown (Bw). If two Bw's mate, use the Punnett Square for F2.

http://en.wikipedia.org/wiki/Punnett_square