Biology : genetics. Help

In rabbits, black fur is dominant over white fur. B stands fr black and b for white.
Question: give the genotype of both patents, if there are 105 black fur offspring, and 38 white fur offspring.
I think it's something with multiplying, but I'm not sure how to. /:

You just have to come up with a possible genotype that could yield the phenotypes given: 105 black fur and 38 white fur.

White can only be displayed as a phenotype if the genotypes of the two parents somehow gave bb. So which genotypes could the parents have to get bb?

Let's try out Bb x Bb. Here's my half-assed Punnett square to show that you can indeed get bb from that cross to get white fur offspring:

. . . B . . b
B . BB . Bb

b . Bb . .bb

(ignore the periods; those were only added in to line up the letters correctly)

So the expected phenotypic ratio here is 3:1 (black to white fur), which means we would expect to get 25% white fur offspring.
That ratio matches up with our observed results. All in total, there are 143 offspring (105 + 38 = 143). 38 out of 143 is about 26%, which is pretty damn close to 25%, so we can deduce that the final answer is..

The genotype of BOTH parents is Bb.