Learn Swedish: Under det våldsamma upploppet använde en åttio poliser sina sköldar. - During the violent riot, about eighty police officers used their shields.

Placing en before a number is a common way to express an approximate amount, meaning "about" or "roughly." So en åttio poliser means "about eighty police officers." Even though poliser is plural, the article en acts as a fixed approximation marker here.

Why does the verb använde come before the subject en åttio poliser?

This is due to the V2 (verb-second) rule. The sentence starts with the adverbial phrase Under det våldsamma upploppet. Because this phrase takes up the first position, the verb använde must immediately follow it in the second position, pushing the subject to the third position.

Why does the sentence use sina instead of deras for "their"?

The word sina is the reflexive possessive pronoun used for plural subjects when they are acting upon their own belongings. It shows that the police officers used their own shields. If the sentence said deras sköldar, it would mean they used shields belonging to a completely different group of people.

Why does the adjective våldsamma end in -a even though upploppet is singular?