How to do Genetic Crossing?

for you in order to get a very good image pull out a piece of paper and darw what i'm about to write out. it makes much more sence drawn out.

first make a square with four squares within it. (2 squaresx2 squares)
above the first two squares write AI BI (one ontop of each box)
beside the two on the side box write i i (one beside each box)

now cross them in the first box you should get: Ai then the box next to it you should get Bi
for the second row you should again get:Ai and then Bi

so looking a your punnet square 2 of the boxes are Ai and the other two are Bi so the answer for you would be

50% would be A blood with recivie O blood trait and the other 50% would be B with recicive O blood trait