ok. im beginning to see where I am going wrong.

the probability that A doesnt scoreandB doesnt concede is always 1

the probability that A doesnt scoreorB doesnt concede is either 1 or 0

The events are opposite sides of the same event in a way.

I need the probability that A doesnt scoregiven thatB doesnt concede, but the formula for that ( conditional probability) involves using (AandB), which I know I cant use because of the reasons above, so I am back to square one again.

Any more help?