Answer:
30%.
Step-by-step explanation:
The probability of getting an Ethiopian with blood type A is [tex]\frac{20}{100} \cdot 100%%[/tex], which equals to 20%, while the probability of getting an Ethiopian with blood type AB is [tex]\frac{100-40-30-20}{100} \cdot 100%[/tex], which equals to [tex]\frac{10}{100} \cdot 100%[/tex] and hence 10%. Therefore, just add the two probabilities together to get 20% +10% = 30%.
Hope this helped!