Acouple has six children. two have blood type a, one has blood type b, two have blood type ab, and one has blood type o. what are the genotypes of their parents?

So, you have a type A, which means one has A, you have a B, which means one has B

So right now, Parent A has a blood type of A, and Parent B has a blood type of B

Now a child has AB, which is a possibility figuring that A and B are options

Now that a child has O, which is only a possibility if both parents have O, the Genotype of your parents are AO and BO.

Hope this helped :)

Could you elaborate?