Olga is married for the second time. Her first husband was blood type A and her child by that marriage was type O. Her new husband is type B and their child is type AB. What is Olga's genotype and blood type?

Olga has blood group type A with genotype IAi (heterozygous)

Explanation:

First Marriage:

1st Husband-Type A (IAi) x Olga - Type A (IAi) = Child-Type O (ii)

Second Marriage:

2nd Husband-Type B (IBIB) x Olga - Type A (IAi) = Child-Type AB (IAIB)

Olga genotype is heterozygous (IAi) this is why her children are having different blood group types.