Thanks for your reply. The correct answer in the book is that there are 2d, 1u, and 0s quarks after the reaction. I understand that the strange number is zero but how can you say 0s if the 2 particles formed contain s quarks? Very confusing.
The net is zero: One strange, one antistrange. 1+(-1)=0. As that net number didn't change for any quark the process is possible via the strong interaction.
