If the union were to call a strike, the situation would become very difficult. => Were....

==>Were the union call a strike, the situation would become very difficult.

Cấu trúc đảo ngữ câu đk loại II:

WERE + S + (not) + O, S + would/might/could + V-infinitive

If the union were to call a strike, the situation would become very difficult.

⇒  Were the union to call a strike, the situation would become very difficult.

* Ta có cấu trúc đảo ngữ câu điều kiện loại 2:

⇒ Were S + to V/ Were S, S + would/could/might + V

* Tạm dịch: Nếu công đoàn kêu gọi đình công, tình hình sẽ trở nên rất khó khăn.

$#Jade$