I wrote it as "the mother of the boy likes tea" am i no good at esperanto ?
Yes, I had to listen to it about 10 times wondering what on earth he could be saying before I figured it out.
It could be a problem with speakers - or try using a different device. It sounds OK to me.
I think this is correct. It sounded like "ktabo" from my phone's speaker, but it sounded much more like "knabo" over my headphones. (It still sounds a little bit off, but that may just be my brain trying to hear "ktabo" now.)
In short, "da" is for quantities. How much bread do you have? Kiom da pano vi havas? I read a lot of books. Mi legas multe da libroj. I want to learn a billion languages. Mi volas lerni miliardon da lingvoj.
"de" is for... well, for all of the other times you would use one of these. ;)
This graphic provides a nice visual. The Tips & Notes also cover these in Da/De and again in Food
I know this is an old question - but no. Neither one is a direct object.
So it seems like the "correct" translation has to be the one you expect people to use in everyday English. This means if you type "The mother of the boy likes tea." You can expect an error message. Despite this sentence being correct, only Spanish speakers would find it 'normal' sounding. A true native English speaker would opt for the short version of "The boy's mother likes tea."
In a nutshell: both are correct but only the one with a possessive 's is going to be accepted here. Even when another example accepts both translations with the word "of" and the possessive 's.