"Where are the boy's pants?"
Translation:Dove sono i pantaloni del ragazzo?
'degli' is for words where the plural article is 'gli' and 'dei' is for words where the plural article is 'i'. So, 'of the men' becomes 'degli uomini', as it is 'gli uomini' and 'of the boys' becomes 'dei ragazzi', because it's 'i ragazzi'. Hope this helps!