Hardy-Weinberg Equilibrium Question
In a population of mice, the presence of black spots is the result of a homozygous recessive condition. If the frequency of the allele for this condition is 0.15, what is the approximate percentage of heterozygous genotypes in this mouse population? (Assume that the population is in Hardy-Weinberg equilibrium.)


We know the frequency of the allele (0.15) and we're looking for the frequency of the heterozygotes. $2\cdot 0.15(1-0.15) = 0.255$.


  (ii) In a population of giraffes, dark brown spots are the result of a homozygous recessive condition. If the frequency of the allele for this condition is 0.10, what percentage of the individuals in the next generation would be expected to be homozygous dominant?


Yes, you are right it is 0.81


  (iii) In a population of monkeys, the allele that causes long hair at the tip of the tail (H) is dominant, while the allele that causes short hair at the tip of the tail (h) is recessive. If 67% of the monkeys have long hair at the tip of their tails, what is the frequency of the dominant allele?


Although the notation is wrong ($p=1-\sqrt{q}$), the result is correct.


  [last question]


As both genotypes GG and Gg are grey, we know that $p^2 + 2pq ≈ 0.45$ (Rather looks 0.48 from the figure though), where $p$ is the frequency of the G allele. From that you can calculate $p$ and $q$ and therefore calculate the frequency of the double homozygous gg