Lol I keep translating this in my head as eleventeen :P :)

I just completed a sentece that used его instead of ему for ages. Why?

can we drop лет in this sentence? or is it mandatory?

Why not Он?

+Vlad we won't use it in documents, anyway. P.S if you're wondering why I didn't reply it's because an error occurs whenever I try to

I said it correctly why wouldn't it take it ?