I came from the army, I am preparing for the EGE. Tasks are delivered...

Three friends study in the classroom – Anya, Vanya, Kolya. The children were given a math tasks at home. Arriving in the class, the children told the teacher the following information: if Anja solved the task, then Vanya did not decide or Sasha solved the task. If the task was decided by Vanya, it was not resolved by Anja and it was not resolved by Sasha. If Sasha decided the task, then she and Vanya decided, well, and so on.

In the place of a teacher, I would have figured out before checking homework, first of all, where, fucking, collie went? And secondly, where did Sasha come from?