In a Hardy-Weinberg population, the frequency of the a allele is 0.4. What is the frequency of indiv

So I have no idea how to calculate Hardy-weinberg equations, such as finding the frequency. Here's an example question:

In a Hardy-Weinberg population, the frequency of the a allele is 0.4. What is the frequency of individuals with Aa genotype?
A. 0.16
B. 0.20
C. 0.60
D. 0.48
E. cannot tell from the information provided

In a population that is in Hardy-Weinberg equilibrium, the frequency of a recessive allele for a certain hereditary trait is 0.20. What percentage of the individuals in the next generation would be expected to show the dominant trait?
A. 8%
B. 16%
C. 32%
D. 64%
E. 96%

Thank you ahead of time :]