These are the assumptions about the conditions in Hardy-Weinberg Equilibrium.

This is the frequency of the A allele in a population with the following genotype frequencies:

AA      Aa       aa

0.60      0.20     0.20

This equation describes the genotype frequencies in a population.

AA   Aa   aa

0.25    0.5   0.25

The genotype frequency in the next generation (given that this population is in Hardy-Weinberg Equilibrium) is this.

This is the frequency of the a allele in the following population: 

(shown as numbers of individuals in the population with a specific genotype) 

AA     Aa     aa

100    200   300