Lol I keep translating this in my head as eleventeen :P :)
Make that One above (над) Ten, and you'll get back on track.
I just completed a sentece that used его instead of ему for ages. Why?
Ages use the dative case emy. Eго would be accusative or genetive
can we drop лет in this sentence? or is it mandatory?
You can. "Ему одиннадцать" means the same. But when one writes documents it is better not to omit the word "лет".
I was so quick with answering that I wrote "He's 18" and it was accepted as 'almost correct'...
Why not Он?
Because Russian uses the Dative Case to express age - I guess you receive the numbers of years, you are the recipient of the years
+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 ?
Я сказал: ему 11 лет and it was incorrect