Если бы они присутствовали на прошл

Если бы они присутствовали на прошлом семинаре, они бы многое узнали о структуре языка

Результаты (английский) 1:

Had they been present at the last seminar, they'd learned a lot about the structure of language

Результаты (английский) 2:

If they attended the last seminar, they would have learned a lot about the structure of language

Результаты (английский) 3:

if they were in the past, the seminar, they would have learned about the structure of language